grizwalter
If you select the entire clip/track, then you can do a one-time drag of the note ends so they are all workable.
That assumes that he drags all the loops in that he will ever need before any editing starts. I think he's saying that he edits as he goes, and has to set durations for every new clip that comes in to the project.
There really isn't any way to automate that, but you can simplify the process by using the Event Inspector. Select the clip, enter a values between 60 and 120 in the duration field, and you're done. There's no need to ever change it back; drum samples are generally played as one-shots, and the note off is ignored.
If it were me, I might devote the time to dragging all the clips that exhibit this issue into a single project, resetting the durations, and re-saving by drag-dropping them to a new location. File naming might be kind of a pain, though.