Hi richied423,
The most accurate and meaningful way to assess the quality and durability of a mattress is by knowing the type and quality/density of all the materials and components inside it because a mattress is only as durable as the weakest link in the mattress and the relative durability of specific materials and components is already well known regardless of which manufacturer uses it in their mattress or how long a specific design has been available for sale. You would need to wait for 5 years or more to be able to assess the durability of any good quality mattress based on customer feedback and even then there may not be enough long term reviews to see a meaningful pattern and the majority of reviews wouldn’t be particularly reliable anyway because a mattress that would be a durable choice for some people may not be a durable choice for others (see post #13 here) and in many cases by that time a mattress may not even be available for sale any longer anyway.
While there is no way to specifically quantify how long any mattress will last for a specific person or predict exactly when they will decide to replace it because it is no longer suitable or comfortable for them (because this is the only real measure of durability or the useful life of a mattress that really matters) and because there are too many unknowns and variables involved that are unique to each person … 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 you have confirmed that it 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 higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” would be higher as well.
There is more information about Casper, Leesa, Helix, and some of the other simplified choice mattresses in post #2 here in the simplified choice mattress topic. and post #1 in the same topic would be well worth reading as well.
I’m not sure where you read what you did but like much of the information that you will read online or in reviews I certainly wouldn’t consider it to be reliable or accurate information. The BME uses high quality and durable materials and there are no lower quality materials or weak links in the mattress that would be a cause for concern in any weight range relative to the durability and useful life of the mattress.
Phoenix