I have found air rifle barrels to behave very similar to rimfire barrels, which is to say, it varies a lot. I think waiting for accuracy to fall off is generally a good routine. If you are a competitive BR shooter, maybe not. But most of those folks know their barrels well, and clean sufficiently to avoid an issue during a match. I use a 9 X 12 box filled with old magazines for a target holder in my back yard. Recently, I had my RAW out, had not shot it in a while so I don't know when the barrel was last cleaned. At 25 yards, the first shot missed the box! The next was only slightly better. I've never had a dirty barrel cause such dramatic results, so I first tested it on the chrono, thinking the hammer might need cleaning and lubricating, but the chrono showed good consistency. I knew from experience there was no pellet clipping going on with the moderator. So, I cleaned the barrel with a few pull-through patches and Ballistol, problem solved, accuracy restored. This episode was extreme, and I still don't understand it, but it happened, so don't underestimate the potential problem from a dirty barrel.