And YES, you can always replace your DSLR with the newest every year or two, and probably need a new set of lenses every few times you do that. A waste of money.
One can replace a DSLR every year or so, but in my experience the only reason is to limit the depreciation hit. It's not like the older models suddenly become non-working. Lenses on the other hand are not going to have nearly the depreciation hit.