I leave the bags on 99% of the time. I haven't found that they slow me down enough for me to tell. Besides, it's better to visit a winery and be able to carry some wine back to the hotel than to have to drink it on the spot and ride back to the hotel under the influence. Right?
There is no way that I'd pay someone to cut my bags down. If I need less storage, I'll take the bags off. I have a expanding tank bag that I tie onto the rear seat and rack if I need storage when I have pulled the side bags off. Even though I do like the look with them off, it does make the bike look front heavy.