At first glance, it seems like a reasonable thing to do. The ratio between playoff and regular season scoring is shown below for ages 18-40:
And it's incredibly rare to play in the playoffs at either an old or young age - 94% of players in the playoffs are between 20 and 34 on January 1st of a given season. A linear fit indicates no relationship between age and scoring ratio, while a polynomial fit indicates a slight difference. Counting all games as equal seems like the right thing to do.