Hi ElizabethKing,
[quote]Final calculations for mattress and foundation- Hard to know if the extra money is worth it.
Spindle-$1329.98
Foam Sweet Foam- $1896.92
Cozy Pure- $2,274.30[/quote]
I’m not sure where your numbers come from but they don’t appear to be correct. I’m assuming that you are looking at a full size and I would also suggest making mattress only to mattress only comparisons as well so that the price of different foundations that are in different price ranges doesn’t skew your mattress comparisons. Any Mattress Underground discount is also calculated on the “mattress only” price as well.
Based on this and on the retail prices that are listed on their sites so you (and any others that are reading this) can make more “apples to apples” comparisons (and not including any discounts or bonuses that come with a mattress) the prices for each mattress would be …
Spindle 10" Natural Latex Mattress: $1149.00
Foam Sweet Foam Urban Green 10" (they don’t have a 9" mattress and their full size is the same as a queen): $1999
Cozy Pure Natural Comfort 9": $1599.00
Unfortunately 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 but 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 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 materials that are higher quality and more durable than the minimum guidelines such as latex (in the top comfort layers especially) it would likely be in the higher end of the range or even longer.
There is also more detailed information about the many variables that can affect the durability and useful life of a mattress relative to different people in post #4 here and the posts it links to.
While a warranty is important to guard against the occasional manufacturing defect in the materials or components inside a mattress … I would keep in mind that mattress warranties only cover manufacturing defects and they don’t cover the gradual (or more rapid in the case of lower quality comfort layers) loss of comfort and support that comes from foam softening that is the main reason that most people will need to replace their mattress. In other words warranties have little to nothing to do with the durability or useful life of a mattress or how long it will be until you need to buy a new mattress. If there is an actual defect in the materials it will usually show up early in the life of the mattress (usually in the first year or two) but knowing the quality and durability of the materials in your mattress is always a much more reliable way to assess the useful life of a mattress than the length of a warranty. There is more about mattress warranties in post #174 here.
Since all the mattresses you are considering use latex which is very durable material compared to other types of foam materials and mattress components … I would treat all of the mattresses you are considering as “close equivalents” in terms of durability.
One of the additional advantages of a component mattress is also that you can replace just the top layer of the mattress if it softens or breaks down sooner than the deeper layers of the mattress (which is likely) or if your needs and preferences change down the road without having to replace the entire mattress.
Phoenix