In case this is useful...
I pitched 2 packets of rehydrated 34/70 into 5.25 gallons of 1.050 wort Saturday morning around 7:30. After 12 hours there was no airlock activity (I did not check to see if krausen was forming). After 24 hours there was no airlock activity and no real krausen (just a couple of yeast clumps floating on the surface). After 36 hours, the airlock was bubbling and there was a thin krausen that didn't quite completely cover the surface of the wort.
I'm going to harvest some slurry from this batch, pitch it into a small starter, and pitch that at high krausen into 5.25 gallons of 1.053 marzen in a few weeks. Hopefully, that will get off to a quicker start.
Edit: I forgot to mention that I pitched the yeast at 55 degrees, and the beer has been held between 53.5 and 55.5 degrees.