I have accumulated over 3k over the past years.

After reading this thread though, it occurred to me that I don't often see a notice of this in chat and then also I realised that I actually forget to commend people.

I just don't think about it, I run as soon as I enter the dungeon, pop sprint right before the first pack, keep running until sprint falls off, AoE everything down, rinse and repeat.
As soon as the last boss dies (usually I don't need any of the loot anyway) I hit U and select leave (faster then manually running to the circle on the end to leave).

I just speed run all dungeons and I just totally forget about the commending thing. Only thing I do is say 'Hi' & 'Thanks, bye' (which are also on macro's because ... faster).