Hi Mike7,
All foam materials (including latex) are basically an insulator and even though latex is more breathable than other types of foam … if there are thicker softer layers that you sink into more deeply and you have an unquilted cover such as the PLB then for some people they can sleep warmer as well. There is more about the factors that can be involved with sleeping temperature in post #2 here and in some cases changing your mattress protector or the type of sheets you use can solve the problem. A firmer mattress would tend to sleep cooler because the softness of the comfort layer is one of the factors in temperature regulation.
You can read more about the many different types of gel materials or gel memory foam in post #2 here and the effect of different types of gel materials on temperature in post #9 here but in most cases gel memory foam will have a temporary effect when you first go to sleep (compared to regular memory foam) and once temperatures equalize the foam would become an insulator.
I would definitely exchange a mattress that is too soft for a firmer version whenever possible because you can make a mattress that is too firm softer with a topper … to make a mattress that is too soft any firmer means you would need to remove and replace some of the layers which isn’t possible with the Beautiful.
The useful life of an innerspring mattress will depend more than anything on the quality and durability of the materials above the innerspring. A mattress will soften and break down from the top down and the “weak link” in almost all mattresses is in the comfort layers of the mattress. There is more about the relative durability and useful life of mattresses in post #2 here.
Phoenix