It depends a bit on a) how experienced a sailor you are, and b) how much time you are able to put into climbing the learming curve.

If you only sail infrequently, it will take a long time, but if you sail most weekends then it will only take a few weeks for you to start to feel more confident about pushing the boat a little bit harder. That's usually when things actually start to get a bit tougher, and you feel you've taken a big step backwards. But that's just because you've raised the bar of your expectations. Persevere through that stage, and suddenly everything drops into place, and you can't imagine why you found it so difficult, and why on earth it took so long to switch to a Contender!

If you are sailing on a regular basis (not once every 6 weeks!), by the end of the your first season, you will feel pretty confident about your ability to handle the boat in most normal conditions.