Hi CooperCanfield,
Post #3 here and the other posts it links to have more information about mattresses for heavier weights that should be helpful. More importantly though I would make sure you follow all the steps in the tutorial post one at a time so you can learn the basics about mattresses (and how to test them) and connect with more knowledgeable and experienced manufacturers and retailers that will already know what you would otherwise need to learn and can provide good guidance about their mattresses.
There is also more about the many variables that can affect sleeping temperature in post #2 here. Latex is the most breathable of all the foam materials and tends to sleep cooler than other types of foam but the type of foam in a mattress is only one of the factors that can affect temperature and as you can see from the two other replies here one person’s experience may be very different from another partly because of the many differences between people (and where they are in the oven/iceberg range), partly because of differences in the specifics of the mattresses they own, and partly because of differences in their mattress protector, sheets, bedding, and room environments.
There are many less people that would have temperature issues with latex than with any other type of foam material (particularly if it uses a cover that has natural fiber quilted with wool) but natural fibers are more temperature regulating than any type of foam.
There is no way to know whether it will last twice as long, three times as long, or 50% longer except in retrospect. Even more important is how well you sleep on it and how long you sleep well before you cross the threshold between sleeping well and “tolerating” a mattress. There is no specific way to measure how long it will be before any particular person decides it’s time to replace their mattress because they can’t “tolerate” it any more and there is a big difference between a mattress that is “just OK” and one that you sleep very well. There is more about the variables that are involved in the durability and useful life of a mattress relative to each person in post #4 here but at your weights I would encourage you to consider higher quality/density materials including in the base layer (or at least in the top 5" to 6" of a mattress).
There is also more about the differences between all latex mattresses and latex/polyfoam hybrids in post #2 here and the post it links to. Post #5 here and post #2 here would also be worth reading.
I would also make sure that you have a more detailed conversation with Dreamfoam since they will be your best source of guidance about their mattresses and the options they have available.
The new layer is shipped to you before you send the old one back and there is a lot less time involved in shipping back a single layer than returning a complete mattress. This is one of the benefits of a component mattress and while they are very good at helping the large majority of their customers make suitable choices the first time … there are always exceptions and there will always be customers who are very glad that they have the option to exchange a layer after a purchase.
I would also talk with them about your firmness choices since they will be your best source of guidance (see mattress firmness/comfort levels in post #2 here).
The Rochester list is in post #11 here but as you probably know I think highly of Jamestown Mattress and they would be well worth a visit. Your personal experience on latex mattresses will be much more meaningful and relevant than any “theory”.
If you are following all the steps and guidelines in the tutorial post one at a time then the odds of making a great choice will be very high.
Phoenix