Ok, so there is not a "correct" answer to this question, but here's my version. I've only been climbing for about 6 months (so I'm not expert), and I was pretty intimidated of leading at first. The first several times I climbed outside (first 2 months were in the gym), I only tried leading a couple of times and was scared poopless. And I didn't really NEED to lead because my main partner would do it all for me. Then I went out with a guide one day to climb some harder stuff on toprope, and after a couple of hard topropes (for me - 5.10 or 11) he made me try to lead something at my toprope limit - which happened to be a 5.11b (at Reimer's Ranch, Tx) I had just done 3 times. Because I was then tired, I ended up not being able to make the crux move and was forced to learn how to fall a few times. The main point I took away from that day was this: try to lead everything - even if toproping is an option. The only way to develop your lead head is to lead. Falling is part of the game, just make sure your gear is good. The added benefit of leading at your limit is that you can develop your climbing and lead games at the same time. And you might be surprised at how well you can climb when you're at the sharp end of the rope!