It's really just an opinion thing, what seems to be the majority of people will stick to slings. They both have their advantages (I gave a bit of a rundown in
this thread). Again, it's your choice, there's no yes or no answer on if you should switch let alone when you switch.
if you are switching, factor in the quality of bow you have, your marksmanship and your ease in producing relatively high quality arrows (minimum quality should be higher than your bow, and your bow should be above 40 for starters in my opinion).