S04 can be SCARY fast. I've had the air lock start bubbling within 2 hours with S04, and finish out in 3 days, back when I was still fermenting without temperature control. It'll push the krausen all the way up to the top of my FF 7.9 with nearly 8 inches of head space on my usual batch size. I always top off to 5.5 gallons and check my OG from there. I wrecked two of the dubblebubble air locks back to back (can't clean 'em out once krausen goes in 'em), so pretty much decided to never use those again. I'll stick with the 3-piece (floating bell) versions. When you guys spund like that, do you still put the off-gas through a trap? Or just vent it in the chamber as the regulator controls pressure? I'm assuming that krausen making up to that nifty little regulator is a REALLY bad thing.
You're right, collecting the yeast can be a little troublesome, unless you have a conical with a removable sediment bulb. I did it a couple times when I was still fermenting in buckets. Keeping multiple yeast strains around starts driving when you brew what, too, to avoid losing the yeast. The cost really isn't that bad, nor really a concern. I did it mostly out of curiosity and experimentation. With the conical, it's easy peasy to collect the yeast. So, if I'm planning a repeat brew, I'll repitch the yeast. You're not the first one I've found that isn't a fan of conicals. My LHBS guy is also a beer judge, and he REALLY doesn't like the conicals, particularly the plastic ones. I've had good service and luck with mine, though, but it is limited in what I can do with it since it is not pressure rated. I'd just as soon NOT be the person that found out how big a mess a FF 7.9 will make when it blows the lid off. Sometimes, a boo-boo is amusing. That would be very NOT amusing.