Hi beertiebus,
Serta doesn’t provide any meaningful information about their mattresses in terms of the quality and/or density of the materials they use so there is no way to make any meaningful assessment about them.
I would also be very hesitant about making an online purchase where there is no way for you to know for certain if this is the same mattress you slept on or how well it matches your needs and preferences in terms of PPP.
Because of all this and the many variables that are involved in the durability of a mattress … there is no way to know how long it will last for you (regardless of how long it lasts for anyone else). You can read more about the relative durability of mattresses in post #4 here. In some cases a mattress may only last someone a few months before they develop “symptoms” on the mattress connected with foam softening that makes it unsuitable for them to sleep on and these would not be covered by a warranty.
The Durango uses higher quality foam than you would find in the Serta and Denver Mattress is a regional manufacturer that is open and transparent about what is inside their mattresses. Many of the Serta comfort layers (which are the weak link of a mattress) are lower density and quality than 1.5 lb foam you are referring to.
Hotel mattresses are often lower quality and worse value than the rough equivalent in the store because they often use a topper or plush mattress pad or bedding package which can be replaced (and helps with the durability of the materials under it), the mattresses aren’t slept on every night so they don’t need to be the same quality/durability, and they replace them much more often than most consumers so their durability isn’t as important.
I personally would never buy a mattress where I didn’t know the quality of the materials inside it … especially from major brands who tend to be less responsive to the needs and requirements of consumers if there are ever any issues.
Hope this helps.
Phoenix