[jon_stggt]

I guess it comes down to what level you want to play at.
In the early days of the big name players today it's often told of 12 hours plus per day.
Common practice from what I can gather is in the region of 5 hours per day. I work on getting 3 hours per day at the moment but am pushing to 5 as soon as I can fit it in.
If you just want to play guitar then I'm sure an hour per day would be cool.
If you have the desire to be a "great player", then kiss goodbye to the clock and just play play play.
This of course is only my opinion.