Anyone have a rough idea of how much could be accomplished on average in 6 months, assuming something like 15 hours work a week?
Simple 2D games require as much as ~40 hours of programming (without any fancy stuff). So, you could assume, that after ~3 weeks you'll have a playable tech-demo of your zelda-style RPG (simple map of the starting location, moving your character and NPCs, maybe transitions between locations or a simple inventory management). If you'll be programming for several months you could have much more time to polish it's gameplay. My advice: go for it, do not be afraid ;)
Edit for the minusing one:
Haps, I do have examples of the fast (about 40 hours) game prototyping, like ones from http://www.ludumdare.com/ and http://www.pyweek.org/ and what about you? Care to backup your minus? ;)