Hi Astronerd,
You probably found the post that is the most “accurate” way to answer your question 
Post #3 here also has some good information.
Part of the difficulty of giving actual years is that durability is so relative to the person on the mattress.
For example I could say that a high quality latex mattress should last 15 - 20 years and a high quality memory foam mattress should last 10 - 12 years + and a high quality innerspring mattress with high quality polyfoam in the comfort layers should last 8 -10 years (and these are of course very arbitrary because it depends on the specifics) but for every person that gives a number then a quick internet search will find many examples that are both much longer and much shorter than any of these. This article for example has examples of latex mattresses that were used for 40 - 50 years but with more modern latex mattresses that use softer ILD’s of latex in thicker comfort layers it would certainly not be the norm for them to realistically last this long. In other cases there have been examples on the forum of latex mattresses that were too soft when they were purchased and within a month it became obvious that they were not suitable for the person using them. If you have a mattress that is “just barely” in the range of what someone needs and it softens only a little it could quickly be unsuitable for that person even with just a little bit of softening even though the materials themselves are far from worn out.
One of the early threads on the forum had an example of a 15 year old convoluted high density polyfoam that was still in relatively good condition. I have a Stress-O-Pedic mattress that has an innerspring and thin layers of foam that is two sided (regularly flipped) and while the foam has compressed and flattened, it is still even and relatively flat and it is currently being used by a 190 lb 14 year old young man with a latex topper and works just fine. So for every “estimate” you make for durability there will be many exceptions to the point where no estimate seems to be correct because there are so many exceptions.
On to your more specific question though …
In your case it probably would. When you are heavier you will “go through” the top layer more and the layers underneath will be more subject to repeated and deeper compression so the durability of the support layer would come into play more than for someone who was lighter. While the biggest difference in a latex support core vs a polyfoam support core would normally be performance more than durability (assuming the polyfoam support layer was good quality) … in your case with your higher weight and depending on the thickness and softness of the latex comfort layers, the durability and softening of the support layers would be a bigger factor for you.
Hope this helps
Phoenix