Hi KSueSmith,
They don’t expire and all you need to do is let the retail or manufacturing member of the site you are buying from know you are a member here (or use the code for those that use one) to receive the discount or bonus they provide (unless there is a temporary sale that is greater than the discount).
The value of a mattress purchase depends on the parts of your personal value equation that are most important to you so the value of some of their mattresses may be much better than others based on your criteria and this may be very different than someone else.
From a “raw materials” perspective though (and don’t forget that buying a mattress based on the price per pound or per inch of material would be like buying clothing based on the cost per pound), mattresses made by the same manufacturer tend to be in a similar “value” range throughout their lineup although mattresses in higher budget ranges tend to have slightly higher margins.
Phoenix