Hi danliang137,
There is no way to predict exactly how long any mattress will last for any particular person in terms of years … only in relative terms (one mattress lasting longer than another). This means that any assumptions that include a specific number of years may not be accurate because it has as much to do with the person as it does with the mattress. You can read more about the many factors involved in the relative durability of a mattress in post #4 here.
As an example to illustrate the point and using a hypothetical softness/firmness scale of 1 (softest) to 100 (firmest). Each person will have a range of options that would provide them with either the comfort/pressure relief or the support/alignment that would be suitable for them and would have a range of mattresses that work well in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). Some people though have a narrower range than others and are closer to the “princess and the pea” end of the scale than the “I can sleep on anything” end of the scale so they would have a narrower range of suitable mattresses and designs to choose from. Lets say for the sake of this example that your ideal softness range is in between 40 and 60.
If you choose a mattress that is in the middle of your range (50) then you have “room” for the foam to soften before it reaches 40 and is no longer suitable for you. This means that if there is 20% softening in the foam that you would cross your threshhold and the mattress would no longer be suitable for you. With very low quality materials such as the Comfort Dreams … this could sometimes happen within the first 30 - 90 days before you have lost the comfort or support you need and you can develop the symptoms that go with sleeping on an unsuitable mattress. Higher quality materials will soften less both initially and over the course of time.
If a mattress you choose is already on the edge of being too soft when you first purchase it (say 40) … then almost any amount of foam softening may put you over the edge. If you choose a mattress that is in the upper end of your range (say 60) … then you have more “room” for foam softening and for you the mattress would be more durable although even here low quality materials will cross your threshold much more quickly than higher quality and more durable materials that will maintain their original firmness for much longer.
You will go through various stages on a mattress over time from sleeping well to “sleeping OK” to “tolerating a mattress” to having more significant discomfort or pain on the mattress and finally deciding that you need to replace it. Most people would typically decide to replace a mattress when they realize that they have crossed one of the last two thresholds (see post #3 here) but others that are more sensitive may decide to replace it when they are only “sleeping OK” depending on their sensitivity … not because the materials themselves have completely worn out (the same mattress may still be inside an “acceptable” range for someone else).
I personally wouldn’t risk the quality of my sleep even for a year with a mattress that used the low quality of materials that are in the Comfort Dreams … especially with your higher weight which will soften and break down foam and other materials faster than someone who is lighter. It would very much be a roll of the dice.
The most important part of a mattress’ quality and durability is the upper layers and the heavier you are the deeper you will sink into the upper layers which means that the quality of the the middle layers also becomes more important than they would be for someone who was lighter and didn’t compress into the layers as deeply. The minimum I would choose in a mattress is @ 4 lb memory foam … and with weights over 200 lbs or so I would be cautious so that the 4 lb foam was relatively thin (say 2" or less) so that foam softening didn’t play as big a role. I would also make sure that the mattress wasn’t already on the edge of being too soft for you which would mean that it may not take very long at all for it to soften and move outside of your comfort and support range.
There are certainly designs that can work well for two people with very different body types or sleeping styles and preferences yes … but only your own experience can know what they may be. You can read a little more about some of the options that could work for you in the first part of post #2 here but local testing with both of you on the mattress is the best way to know. If this isn’t possible then more detailed phone conversations with knowledgeable and experienced online retailers or manufacturers is the next best way to choose because they can use their experience and the “averages” of their customers that may be similar to help you make better choices which can improve your odds of success if you are inside the averages. The knowledge and experience of who you deal with and their ability to help you make “educated guesses” based on the information you provide them about which of their mattresses may work best for you can be one of the most important parts of making a suitable mattress choice besides the quality and value of the mattress.
This relates to the last question and is certainly a possibility yes. Again … it would be important to choose a design that had better odds of working for both of you and for any changing needs and preferences down the road. A mattress that includes the ability to make changes in the future either with individual layers that can be re-arranged or replaced or from local manufacturer that can make custom adjustments to a mattress at a reasonable cost can both be good options and allow you to make some changes to the mattress rather than replacing the whole mattress. Of course all of this is part of the tradeoffs that are involved with any final decision and which of the many criteria that may be most important to you are the most important parts of your personal value equation.
The materials you choose in your mattress are a personal preference and there is no “should or shouldn’t” involved in these types of choices or any preference choices. Regardless of which type of materials or mattress design you prefer though … all materials have better and worse quality versions (more or less durable) and I would focus on choosing the best quality and most durable materials available inside your budget range.
Post #13 here includes my thoughts about reviews. While it can be useful to use reviews to indicate the level of knowledge,service, and experience of a manufacturer … I would pay little attention to reviews about anyone else’s experience on a mattress because each person’s experience is unique and may not apply to you. A forum search on Rocky Mountain Mattress will bring up more posts and information about them and as you know they are a manufacturing member of this site which means I think highly of them and they are among the best quality/value available.
Phoenix