Hi Harper,
BedBoss has some good value mattresses and as you mentioned they are CertiPur certified so as long as the model you are considering meets the memory foam criteria in post #10 here and you are comfortable with some of the uncertainty of buying a Chinese memory foam mattress (see post #2 here and post #6 here) they can be a good option … as long as you can confirm the quality of all the materials in the mattress.
I would tend to make sure they can provide you with the specific density of the memory foam and the retailer should be able to call his rep and find out for you. There is a significant difference between 3 lb memory foam (which is low quality and would be less durable) and 4 lb memory foam (which is medium quality/density and would be more durable) so I would want to know where it was in that range. I would also want to know the density of the memory foam topper.
In some cases … depending on all the factors that are involved in the durability of a mattress (see post #4 here) … lower quality materials can soften or break down to the point where they no longer provide the comfort and support that you need more quickly than 3 years but of course each person may have different criteria that are the most important parts of their personal value equation.
Phoenix