Really, I find that whenever I want to learn a new trick I just see how I feel on the day as it is that that will ultimately decide whether you will do it. For instance there could be a day where you say you really want to land a switch front board but on the day rails aren't working for you so instead of just getting anoyed and hurting yourself, just get the kickers and land that 540 instead.
Basically my advice for learning any new trick is that unless you are super stoked to learn it and have the trick dialed in your head then wait until you do.
If you don't have the time for that then just get super syked and go for it, whats the worst that can happen?