Hi yubbers,
The density of the latex is a “comfort spec” and isn’t particularly important although I would want to know the type and blend of the latex so that you can make more meaningful comparisons with other mattresses.
I would also check the law tag to confirm that latex is a significant percentage of the materials in the mattress (based on weight percentage). If the specs are correct the latex should be somewhere in the range of 40% of the contents of the mattress. The law tag should also indicate that the mattress is using all new materials.
One of the red flags is that the manufacturer told me that this mattress would normally be selling at twice the price and if it is a new mattress with new materials and isn’t a comfort or warranty return and they are an authorized dealer then I would want to know why they are selling it at a price that would be closer to their wholesale price than the retail price that would normally be charged to consumers. Something just doesn’t add up.
The single biggest factor in the durability of a mattress is the quality and durability of the materials and components inside it … not the thickness (see post #2 here).
While there is no way to quantify how long any mattress will last for a specific person or predict exactly when you will decide to replace it because it is no longer suitable or comfortable for you (because this is the only real measure of durability or the useful life of a mattress that really matters) 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 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 (in the comfort layers especially) it would likely be in the higher end of the range or in the case of the mattresses you are considering the chances that you would have additional “bonus time” would be higher as well.
There is also more detailed information about the many variables that can affect the durability and useful life of a mattress relative to different people in post #4 here and the posts it links to.
Phoenix