But how many people have gone the D-League route and then made it to the NBA and were anything more than an end of the bench player? HOw many from Europe?
This "Old" for NBA thing is not even a big deal. This is not the NFL. If he becomes a solid journeyman player he likely will play 7-10 years. Mika just turned 22. If he comes back he will only be 23 when he goes into the draft. If he is drafted with guaranteed money he will likely stick, barring injury. If he is good enough to stick for 10 years he will be 33 at the point of retirement. You have a lot of end of bench players that play for a very short time, but the guys with the skill-set to play significant minutes stick around for a lot longer.
Lots of this depends on his durability and luck with regards to major injury.