I find that fermenting 1968 on the colder side (low 60's) seems to yield the cleanest flavor / decent attenuation.
however, I find that sometimes 1968 has a tendency to shut down and fall out, leaving beers under-attenuated.

For years I was fermenting in a basement where ambient temps were in the high 50's low 60's. Beers usually finished as they should, sometimes fermentation took longer, but that was mostly good. Then one week before summer started there was a huge heatwave. The beer was a 1.062 OG american IPA, cooled to 56-58 degrees. I pitched one 16 oz mason jar of 1968 harvested one week prior. I checked the beer a week later - the ambient temp of the basement was in the high 70's! This beer was probably the best beer I've ever made.

Is that what 1968 really needs? start cold - 58 or so, then continuously ramp up to 70's over a week??

That would be my vote. Start around 60-62degF and after a day or two of active fermentation, slowly ramp up to 68-70 to keep the yeast in solution as long as possible before they turn into a sludge on the bottom of the carboy.

Should give clean(ish) flavors for an english yeast, good attenuation and clear beer.

I start it at 65 for 3-4 days then let it ramp up to 70 for a few more. I do something like this for all my beers just with different time scales/temperatures. The cool temp at first sets the flavor then the warm helps it finish attenuating well.

We are following the same path as Ziggy. This stuff flocs so hard, I am not sure you want to go too cool, and you need acivity at the end for a Diactyl rest.

Yes, that seems to be the challenge with 1968 - if you want cleaner flavors you want to start cold, but if you miss the point where it starts slowing down and dropping out you're kind of screwed. I wonder what the pros do when yeast drops too fast - blow Co2 into the bottom of the conical to rouse it?

So when is an ideal time to ramp up from colder temps? When half gravity has dropped? 3/4? Or maybe there's a more convenient way to check - just as krausen starts to fall?

Maybe I just got lucky that one time - the yeast was a repitch, so cell count was high. It probably got right to work as soon as it hit the wort @ 58 F, the exothermic fermentation probably raised it 3-5 degrees for about 2 days, and then the heat wave hit and wort ramped up to the 70's and finished out. Dumb luck.

I hate it, I brewed so many beers concentrating on ingredients, yeast, water, etc but the biggest thing I didn't focus on was controlling fermentation temps. Arrrrrrg.

But now you know, and knowing is half the battle. http://www.youtube.com/watch?v=pele5vptVgc

...half the bottle...Knowing is half the bottle!

One more vote for pitching in the low 60's and then ramping up after a few days. I like to let it get up to at least 70, and have had it up to 74 at the end of fermentation. Great yeast flavor.