3 hours a day over a year - definitely some dedication right there.
In my opinion, UMAT isn't really something that you can study for 1 hour a day over a year's span.
I think it's more doing timed past papers to develop confidence, speed and a feel for the test.
I'm likely doing the exact same thing that your going to be doing.
But if I was to do UMAT next year, I'd only start studying for it after the GAMSAT. 3 months study for the UMAT is plenty of time.
For the GAMSAT, I'd be looking to do routine based study as you suggested.