Hi Kmfl98,
1.8 lb polyfoam is a better quality polyfoam than most major manufacturers use in their comfort layers and in general is getting into the lower end of higher quality polyfoam. It is in a density range that is often found in better value traditional mattresses but not in premium budget ranges where you will usually find more premium foams like HR polyoam, latex, and good quality memory foam.
Durability though can’t be assessed by a single layer alone though because of all the variables involved because it depends on the rest of the mattress and how it is constructed (tufted, one or two sided, etc) and on the many other factors that are part of durability that you can read about in post #4 here. In terms of “value” … it is also relative and also depends on the budget you are in and how the mattress compares to others that are available to you and on the “tradeoffs” that are most important to you (see post #2 here).
Any foam or component can be “acceptable” by itself depending on what else is in the mattress and on the construction, design and budget range you are in but in general terms I would certainly consider it if I was in a budget where HR polyfoam or latex was or other premium materials and components were not available to me. 1.8 lb polyfoam in a mattress made by a good local manufacturer who stand behinds their mattresses and has the knowledge and experience and integrity to be able to tell you from their own experience how long you could reasonably expect it to last can certainly be part of a durable mattress and would probably be better quality and value than most of the alternatives that are available to you.
Phoenix