[parse_tree]

In my experience, LONG practice sessions are much more effective than short ones. E.g., I've found I get far more out of one 8 hour practice session than four 2 hour sessions.

I'd also say you need to do it intensely - you've got to be into and "feeling" what you're doing. If you're just sitting there waiting for your 3 hours of "practice time" to elapse so you can go chill you may as well just not do it.

[andymism]

The value of very long practice sessions probably depends at lot on the skill you're trying to acquire. If it's a mechanical/physical skill, then the muscle groups involved would be a big limiting factor, especially for novices. Playing guitar would be challenging for a novice to practice for more than half an hour while people of average physical ability could practice a golf swing for an hour or more on day one.

The problem with favoring long sessions is that you can fall into the trap of only doing long sessions because of the perceived efficiency. Which means you'll need to 'make time' for it. Which means you'll put it off. The result is that most of the gains you make will be lost by the next time you find time for another extended session.

[parse_tree]

Yeah, good point, my advice is not particularly general. I guess I should also add, I've found most things not particularly enjoyable until I get a minimum level of skill. So if your a complete beginner jumping in for 10 hrs at a time might be a little much.