I brewed a blonde ale 11 days ago and pitched two packages of the yeast after rehydrating in a half cup starter. The thing kicked off extremely fast. I had full fermentation within 12 hours or less
first off, when you say you "rehydrated in a starter" - you didn't really make a starter did you? All you really need to do is sprinkle the yeast on the beer and give a swirl, though rehydrating in 80-90 degree water can help insure closer to 100% viability (but as much as you pithed that was certainly not necessary.) Regardless, any form of starter for dry yeast can actually be detrimental.
Also, 12 hours??? What temp did you pitch and ferment? I pitch US-05 fairly cool (low 60s, high 50s sometimes) nd keep very cool fermentation temps. I use it regularly and for me this is a slower fermenting strain. Overpitching and pitching warm can certainly accelerate fermentation - but 12 hours is crazy short. As you probably know an extremely short fermentation does not necessarily make the best tasting beer.
Also, I am planning a brew in my conical with US-05 and I plan on harvesting it for the first time, simply because it has started to get kind of expensive - I used to be able to get it for 2 bucks a pack. Now it is nearly 4 (or more depending your retail location). I don't anticipate any issues with it. I certainly would not go on an entire yeast cake with a low gravity beer though - you only need 1/4 of the slurry for a 1.050 beer.