Hi Mattressthiyear,
The foams they use are CertiPUR certified so offgassing shouldn’t be an issue unless you have a specific sensitivity to polyfoam (which is the type of foam that are in most sofas and upholstered chairs). Most new mattresses will have some initial odor but it will normally dissipate quite quickly and I haven’t seen any comments about the Tuft & Needle having any unusual issues regarding how it smells.
The Tuft & Needle Five mattress has only been available for a little more than a year (and the Ten significantly less than that) and since 1.8 lb - 2 lb polyfoam will last much longer than a year for the large majority of people regardless of which manufacturer uses it in their mattress, it’s still years too early to use customer feedback as any indication about the durability of the mattress. There is more about the many variables that can affect the durability and useful life of a mattress relative to each person in post #2 here and the most reliable way to assess the durability and useful life of a mattress relative to other mattresses you may be considering would be based on knowing the quality and durability of the layers inside it (see this article).
I would also be aware that each person’s experience on a mattress can be very different from someone else so I would take any reviews about a mattress (either positive or negative) regarding comfort or durability with a big grain of salt (see post #13 here).
It certainly uses good quality materials and there are no weak links in the mattress but when you can’t test a mattress in person before a purchase and there is only one firmness choice then it is really an “all or nothing” choice where either your own sleeping experience will tell you that the mattress is a good “match” for you or you can return or donate it and receive a refund at no cost or risk.
Phoenix