Neglecting my babies for the weekend...

[Stinkfist]

Thanks for the responses guys.

I know this might be an "it depends" kind of question, but at what point(s) does it become safe to let the temperature rise? Is it OK at 40% attentuation... 50%... 60%... 70%?

Are the majority of high temperature off flavors produced during the first half of fermentation? Assuming ale yeasts.

I think 80% is a good time to let it start to free rise...

[HighCountry]

I'm pretty sure that off flavors are primarily created during the yeast propagation phase. I don't think it's recommended to let the fermentation rise too much, but as long as the propagation phase has completed, you can let the temperature rise a reasonable amount. The fermentation will finish more quickly, and thus the diacetyl reuptake will happen efficiently and quickly. I think the biggest risk from letting the beer warm up to 80 degrees for too long would be the promotion of staling reactions. No matter how good your process is, there's bound to be some dissolved oxygen in there, especially if it's in a carboy with a fermentation lock. If you could keg it and get it under CO2 pressure before you leave, flushing the O2, that might reduce some of the risk of undue oxygenation.