I was already substantially proficient in theory before I started learning the piano, but I can't tell you how much it helped to actually experience it on the instrument. I wouldn't recommend devoting so much time to it (Even though it is definately important), I'd suggest you get a short and sweet theory book (Not the big quasi philosophical ones by Piston and Schoenberg, unless you REALLY have your mind set on becoming a composer) maybe find some time to read through it, and then examine the sheet music for the pieces you play, especcially the ones you're paticularly aurally familiar with, and discover where the chords, scales, modulations et al really come into play.
While theory definately IS important to any musician, if you've got your mind set on being a player rather than composer I wouldn't suggest sacrificing so much time for it.