Hi blwis,
Some of my thoughts about Luxepedic are in post #9 here.
I certainly hope not!
If you figure a 10 year lifespan for a reasonable quality memory foam mattress then the odds are pretty good that you will need to buy another one 
Buying a mattress online can also be more “risky” than a local purchase where you can test the mattress for pressure relief, alignment, and any other preferences you may have in person. If you let me know the city of zip where you live I’d be happy to let you know of any better possibilities I know of in your area that would give you a chance to do some local testing. ADDED: I see you’ve already done this in your other thread and I’ve linked to the list of the better choices in the SF Bay area in the other post where you have some very good options available.
Other good online sources of memory foam mattresses (that meet all the criteria of providing complete information about their mattresses including the quality/density of the foams and are CertiPur certified) are in post #12 here.
If you haven’t slept on memory foam mattresses before I would strongly suggest that you test some out in local stores before buying one online because they can be a “love it or hate it” material and are very different from more traditional fast response foams. There is more about some of the pros and cons of memory foam in this article.
As for an adjustable base it really is a matter of preference and whether any benefits are worth it to you. We have one (a Reverie Deluxe) which we really like and while it certainly isn’t a necessity … it’s great to have as a “luxury” for watching movies in bed, reading, or even for the occasional “massage” (although it isn’t exactly a real massage :)). For those who would benefit from it’s more health oriented benefits (such as to help with acid reflux, snoring, or other health concerns where elevating the legs or torso may help) it would certainly have even more value.
Phoenix