I would say for a month or so. This year I was abroad for 2 weeks or so and pretty much missed the whole season . Offcourse if you enjoy it so much then you can always check the webcams on troodos before going.
Our guidebook said december till april. Sounded like mid december to mid march though. We went up last week and it looked a lot like the above picture. But a lot of it is now turning slushy. The ski resort apparently closed down the week before or so. It's not exactly the place to go for skiing, but a good novelty when you live next to the sea and it was 21 degrees when you left the house. ie. it was bloody freezing up there. Wish I had taken my gloves.... if I had any....