Hi nameless1,
You can see some pictures of the Morgedal firm and medium mattresses in post #3 here. While the base layer is 2.2 lb polyfoam which is a good quality material … the top layer of a mattress is normally the weakest link in a mattress because it is the layer that is most subject to the constant compression and deflection that is the main reason that foam will soften or break down over time and the top 4" - 4.5" layer in the Morgedal is 1.7 lb polyfoam which is a little lower quality/density then the 1.8 lb polyfoam that I would normally suggest as a minimum guideline for comfort layers (although it’s better than most mattresses in a similar budget range).
You can also see a picture of the Morgongava in the same link. It is an all latex mattress and uses a blend of latex that is 85% natural and 15% synthetic. Latex in general is the most durable of all the foam materials so there are no lower quality materials or weak links that would be any cause for concern relative to the durability and useful life of the mattress.
There is more about the 3 most important parts of “value” of a mattress purchase in post #13 here which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on suitability, durability, and all the other parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
While there is no way to quantify how long any mattress will last for a specific person or predict exactly when you will decide to replace it because it is no longer suitable or comfortable for you (because this is the only real measure of durability or the useful life of a mattress that really matters) because there are too many unknowns and variables involved that are unique to each person … if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new (see post #2 here) and you have confirmed that it meets the minimum quality/durability specs that are suggested in the guidelines here then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” would be higher as well.
There is also more detailed information about the many variables that can affect the durability and useful life of a mattress in post #4 here.
Assuming that you have done some careful testing on the Morgedal and have confirmed that it is well inside the comfort/support range that is suitable for you … since the foam density of the top layer is a little lower than the recommended guidelines, it would be reasonable to expect that it would only maintain it’s comfort and support for less than 7 years although how much less would depend on how sensitive you are to any foam softening over time that would affect your support/alignment on the mattress. I would keep in mind that foam softening and the loss of comfort and support is the most common reason that you will need to replace a mattress (even if there aren’t any visible impressions that are deeper than the warranty exclusions) but since the density of the top layer is only a little lower than the minimum it’s possible that it could last you for 5 years although this wouldn’t be a certainty.
Again assuming that you have done some careful testing on the Morgongava and have confirmed that it is also well inside the comfort/support range that is suitable for you … since it uses latex which is a very durable material then it would be reasonable to expect that it would last you closer to 10 years and the possibility for “bonus time” after that would be higher as well. It would certainly be a much more durable choice than the Morgedal.
Some of the better options or possibilities I’m aware of in and around the San Francisco/Berkeley/Oakland areas (subject to making sure that any mattress you are considering meets the quality/value guidelines I linked earlier in this reply) are listed in post #2 here.
I would also keep in mind that the most important part of the “value” of a mattress purchase is how well you sleep on it and on how well it matches your unique needs and preferences in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your Personal preferences) because there would be little value in a mattress purchase that you don’t sleep well on regardless of it’s price or the durability of the materials. A mattress purchase and how well and how deeply you sleep on the mattress you purchase will have a bigger effect on your overall well being (both waking and sleeping), and on your mental and physical functions and recovery than almost any other purchase you will make over the course of the next 5 - 10 years.
Phoenix