I don't think you appreciate how good a player Speights is. He has the highest PER of any Sixer. As objective measures of a players production go, PER is one of the best, and the best players have the highest PER score.
He hasn't hit a wall, last night in 18 min. he scored 10 pts on 5 of 9 with 3 boards and a block. Assuming that he can maintain that PER playing more minutes, he projects to score 20 pts and more than 6 boards in 30 min. There is no reason to think that he can't play at that level until you see how he reacts.
He has the highest PER of any rookie, and if he was playing starter minutes he'd be a ROY candidate.
So in spite of his mistakes and limitations as a player, he's far more productive than Sam, Reggie, Donyell or Theo. And, he's only going to get better with experience.
The best way to improve a player is to play him an evaluate the weaknesses you see. You can't see the weaknesses unless you play him, and then teach him how to correct his play. The more things you ask him to do, the more you see what he can and can't do, and you can also see how fast he learns from your instruction when he plays.
What you don't want to acknowledge is that every player should earn their minutes based on how they produce. Players who score more points on fewer shots, in fewer minutes, and get more rebounds and more blocks and more steals deserve the playing time. Speights by his play DESERVES more minutes than any other player on the team!
I'm not worried about him burning out. He is excelling in the minutes he's given now, and the next step is to see for how long in a game he can produce at that level. We're talking about a 20 and 10 power forward here, exactly what the Sixers were hoping to acquire when they traded for Elton Brand. He fills a need the Sixers have and should be used in that role to the extent that he is capable. He projects to be an all-star in the NBA and was a real steal in the draft.