The goal is to have an infinite window of contention. A team that has the chance to make the playoffs every single year. Get this "1 year window" crap out of your head.
What happens if Donaldson and Tulo both get injured next year and miss 100 games each? Then we would be f***ed. If we build a team that is competitive EVERY year, then we don't waste the "1 year window" thanks to injuries.