don't worry about the amount of tables you are playing, 4 is enough for someone at the micro's imo, anymore and you just don't learn as much whilst playing, things like blind stealing and 3betting from the blinds need to be learnt on less tables as they are much more villain dependant, for example, your in the SB with A7o, folded to the CO who raises, BTN folds and its on you, playing 12+ tables this is an auto-fold, b/c you dont get tricky all that often whilst playing 12 tables, playing 4 tables however you notice that the guy in the CO is very positionally aware and has a much wider raising range in LP than anywhere else......... so he raises a lot of mediocre
hands basically, you have an ace so you have a blocker to hands like AK/AQ/AJ that might raise there, his range for calling a 3bet is a LOT tighter than the range that calls a 3bet....... so 3bet!!