My experience is about the same as Robert, although the farthest I taken a yeast is 13th generation US-05. Last evening I did a starter of 9th gen. 34/70 for the Chili Lager I'm brewing today, I had bubbles every 4 seconds 4 hours after pitching. I usually only dump a harvest when it gets autolytic, had to dump 2 jars of 05 last night that were only a couple months old.
Update. FWIW I had to dump the last 2 jars of harvested 05 yesterday because they were showing definite signs of autolysis, one was only 3 weeks since harvest. Could be coincidental but all of the harvests from the most recent generations started getting autolytic in a fraction of the time I would normally expect from 05, but could also be a result of serial re-pitching. Anyone else have this experience this?