Hi MemFoamBlues,
I think I would probably hesitate to buy a whole new mattress that was only a year and a half old and otherwise was working well for me unless I had looked at and seriously considered other options first. Post #2 here along with post #29 here talks in more depth about regulating temperature and it could well be that making some other smaller changes (such as the protector you were mentioning) would solve the problem. The memory foam Simmons uses in the Comforpedic is a more breathable type (relative to other memory foams) so along with a few other adjustments may be enough without having to go through the frustration of buying a new mattress.
I would go layer by layer first of all and see which layers (that you could change) could be contributing to the problem. While you couldn’t change the foam or the quilting and ticking in the mattress … you could change both the protector and the type of sheets and bedding you were using (unless they were not contributing to the problem).
If your mattress is on the softer side and you are sinking in a little more than you would be with a firmer mattress and you have some “room to maneuver” in the pressure relief qualities of the mattress … then a protector that has a slight effect but not a significant effect on the memory foam (like the Dormeir) may be well worth considering.
You wouldn’t really be “out” the amount of a new protector because you could use it on any mattress you purchased and no matter what mattress you had it would be more breathable and temperature regulating than the protect-a-bed and would be an improvement. You wouldn’t be out the amount of the Dormeir so much (or another protector) as what you spent on the protect-a-bed and because you are more sensitive to heat issues changing to a different protector may be a good idea anyway regardless of mattress.
Latex as a category is the most breathable of the foams (Talalay more than Dunlop) so at least this would be an improvement but once again it’s only one of the parts that could affect temperature and the others could still cancel out its benefits.
Coils are the support component in the deeper parts of the mattress and they still have foam on top of them so it’s the foam or other materials in the top layers that will have the biggest effect on temperature … not whether it has an innerspring or some type of foam as the support layer. It can make some difference (depending on how much and what type of materials are above the coils) but not as much as the layers that are closer to your body which are the main layers that control temperature regulation.
The longevity of a mattress will also be primarily dependent on the comfort layers of the mattress which are typically the weak link of a mattress. In most cases (with a few exceptions) the coils are more about performance than about durability although they could also have an effect as well especially with thinner comfort layers where the coils are subject to more compression and wear. Knowing the quality of the coils at Ikea would depend on knowing more information about them than they provide on their website but in most cases they use relatively lower coil counts in each category of coil (which is only one part of the quality and performance of a coil) and I would put them as a group in a more "budget quality " range. You can see some of my thoughts about the latex mattresses or latex hybrid mattresses there in post #3 here.
Warranties are very misleading and not really connected to the life of the mattress because they don’t cover the loss of comfort and support that is the main reason people need to replace a mattress. they only cover manufacturing defects which will generally happen in the first few years of ownership.
Again in most cases the coils are more about performance than durability but once again it would depend on knowing the specifics of the coils in a particular mattress. In most cases … I would be looking at the effect of the coils on PPP (Pressure relief, Posture and alignment, and Personal preferences) rather than their effect on durability. As you can see in this article and in post #10 here … coil counting or comparing coils (other than with your body lying on the mattress) is mostly a waste of time unless you are also comparing the other specs that are part of the coil as well which in most cases you won’t be able to find out. I should also mention that RoomandBoard itself isn’t a “recommendation” but just a potential source of better quality/value mattresses but like every other retailer or manufacturer on the lists around the forum this is always dependent on your ability to find out the details of what is in a specific mattress you are looking at. They also carry some mattresses that use foam densities that are so low that I wouldn’t consider them. Everything always depends on the specific mattress.
But back to your original heat question … I would first identify all the layers above the mattress and whether you may be sinking more deeply into the foam in your mattress than other mattresses before deciding what to do next.
Hope this helps.
Phoenix