Are the Heat Reserving themselves for the playoffs?

I truly believe the Miami Heat are reserving themselves for the playoffsand not playing to their full potential.Lately they have been playing great defensively plays and are getting back to their old style. On Thursday was the first game of season they were dominating the entire game with no problem of catching up in the second half. They played against dallas who is playing a decent game without Dirk.
The Miami Heat starters rested the entire fourth quarter and the bench played a decent game to the point Dallas was catching up and the heat won by 15 points. In order for the heat to win games from now on is for the bench to improve on defense and offense and get more playing time.