How long is constant temp important?

I've got a batch of Rolf's Irish Red Ale happily bubbling away in my fermentation chamber. I pitched notty on Sunday, and am holding the temp at 18*C (65*F). I usually ignore a new batch for a solid 3 weeks before bottling, but I'd like to do another batch ASAP, and I'm wondering how long constant temp control is important.

When should I take it out and let it ride the remaining time on the counter (temp swings between 16 to 20*C). I'm thinking after the krausen falls I can probably shelf it, but I'd love to get another opion.


Cheers

First 72 hours of active fermentation temp control is crucial, but since yeast often has a 3 day lag time, I recommend folks maintain temps for the first week. After that it's fine.