It's not a good idea, it's the best idea. I've actually done it, and that's how I've seen other people doing it. I left because my health was bad and I had trouble to cope, but God willing maybe I'll be a monk one day anyway, wherever he wills although Athos would be my first choice again.

The longest I ever stayed on Athos was about 3 months. People come all the time day and ask to stay, then suddenly they complain it's too hard, or they just disappear and leave the monastery after a few days, the better ones quit after a couple weeks.

Don't make too much plans, visit a holy place is always good. Talk to the elders / priests / monks there and see how it goes. Don't be surprised if it doesn't go.