You know what they say about the three most dangerous times in flying:
100 hours: you know nothing
1000 hours: you think you know everything
10000 hours: you've forgotten everything
I fly with a UAS, and they have a currency of 31 days for most essential skills (aeros, stalling, spinning, etc). I would say that is about as far as I'd like to go. I have flown before near the edge of the CAA/JAA currency limits, and you don't inspire yourself with any confidence if you havn't flown recently. I think anything outside a month and you are really pushing it.