In the early days, maybe 6 - 12 months between punts, because of circumstances such as the area I lived in, work, family, money etc not to mention the difficulty of finding a decent SP.
Since the advent of AW, I once went 12 months without a punt, when I thought I'd give up. Once a punter, always a punter though and for the past 5+ years it's been up to 3 months between.
Shortest time between punts was 2 hours, when I booked 2 punts in Milton Keynes parlours, 12pm and 2pm