Ferment cool for how long? When to let it ramp up?

I've been fermenting for the past few months with Safale-05. I've used it for nearly every beer I've made this spring/summer (stouts, IPA, IIPAS, cream ales, strong ales) -- except for a couple of spring hefe batches and the Kolsch I just made.

I'm using a water cooler and ice bottles (underneath an a/c vent) to keep my fermentation temp at 60-61F. I've had excellent results by swapping in a single water bottle to keep the temp stable. I'm routinely getting anywhere from 75% to 87% attenuation (granted, I've been mashing for 90 mins, so this may have something to do with it, too).

Now, I'm fermenting a Belgian white (with 05 again -- so an 'American White' I guess) -- but I'm curious: what's the critical fermentation period for the yeast? Can I let it ramp up on its own after 72 hours?

I've been assuming it's the first 72 hours or so -- but I've been hesitant to let the temp rise on any of my ferments except after 10+ days. It struck me yesterday when I was looking at my fermentation that it's been 96 hours @ 60F and I've got a nice, four to five inch head of krausen on my 'American White'. I took out the water bottle, and after about 12 hours by this morning it ramped up 65F or so -- still an okay temp, I know, but it's higher than I've been doing -- but I'm still curious about the 'critical window' for the yeast. (No, I haven't checked it yet -- I'll do that tonight to see where I am in the fermentation.) I mentioned this another threat, but Safale-05 gives off a definite peachy smell when fermented this cool that (in my experience) dissipates pretty quickly once bottled.

I've heard Jamil and Tasty on CYBI talk about letting yeast ramp up by itself after several days -- but I'm hesitant to try it too early in the fermentation. I know if 85% or so of the fermentation is complete, i can let it warm to finish out the attenuation. I know I can test it and estimate how far along the fermentation is -- and I know this is the best way to know for sure -- but is it overkill to keep the yeast at 60F for 10+ days? Is 3-4 days enough in a controlled environment? What's the general sense? Does it depend on the yeast strain? Or is there a common point among all yeasts when its done what its needed to do in the cool environment and is no longer so temperature sensitive?

I'd say it is definitely dependent on the strain. The side reactions are what you are inhibiting with the low temperature, and those side reactions are very, very characteristic of the species, strain and even batch number (as Danstar found out with recent batches of Notty).

You're doing a Belgian white, but you don't want any ester-y flavors or side reactions? You're making a crisp-tasting Belgian? Ooooooookay... "different strokes for different folks" and all...

I likes me some esters, so I would've brewed the whole batch a lot closer to 70F from the start. That's just me!

For my ales I typically temp control for the first 7 days, then let it ride after that. I don't usually take a gravity reading until at least 21 days in. So far so good for me.