I use two of the bump n' go trolleys on my club (National Capital Trackers) module. Figure they run about 8 hours a day over a weekend, sometimes more. Especially at Christmas time, they may run 8 hours a day for a week or more.
I've got two BnG trollies - an MTH Railking and a cheapo (but new in the box free!) Lionel Village Trolley from the 1990s. I've been running them with cheap DC transformers from Bachmann HO sets. Running under DC, I've found them to overheat the transformer pretty easily at times. For my longer displays, I'll have to pick up a basic AC transformer in the future.
In terms of reliability - the MTH trolley is awesome. Runs all day and I can get it down to a reasonably slow speed so it isn't smashing into the bumper really hard. I tend to prefer this for shows not only for the slower speeds but it also has pick up rollers and isn't as sensitive to dirty track.
The Lionel is very light weight and must run faster to keep from stalling. It has slide skates, not rollers and those can be finicky on dirty track. However it has a much smoother bumping mechanism so running it faster doesn't result in damage although it sometimes has a tendency to not fully engage the motor on each bump causing it to stall. You can see the Lionel one in the above photo. That show was a week-long event so we had several to swap out. My "neighbor" is a very close friend of mine and had his MTH Santa Hand Car and Trolley so we also swapped those out regularly. It was nice having several holiday themed pieces to run.
Generally for a weekend event, I'll usually just stick with the MTH trolley. For longer events, I'll take both to a show and swap them out every few hours/days.