Brewed a test batch (3 gallons) that had an OG of 1.081. I know US-05 can handle this easily with one packet, but I pitched 1.5 for some reason. Did I overpitch?
I personally believe it's very difficult to over-pitch (within reason).
I did find this quote from someone at White Labs:
If the beer is overpitched, yeast do not grow though a complete growth cycle. This results in few new yeast cells, which makes for unhealthy yeast and low viability by the end of fermentation.