I would probably say 3 months on a downswing- followed by 2 months of bad poker playing- playing my draws too much, trying to gamble with AQ vs. a small pair pre-flop and losing, etc.
At that point I took a break, did other things besides poker for a week, read a couple
poker books, watched some televised poker and railed for about 2 more weeks - after I did that, I reloaded and haven't looked back. I have had periods where I've gone card dead and had to step down in limits and grund it out- but thankfully nothing real dramatic thus far.