prefix filtering per IRR - practices

Hi, I have a question regarding what's the most common practice [1] for transit ASs to filter prefixes from their BGP customers when using IRR data. (which of course everyone does...) Would many/most/all/none : a) accept only the prefixes listed in route objects or b) accept these and anything "upto /24" (or "le 24") I was hoping / assuming the latter but I start getting a different impression. Yep, and apart from the current status, the tendency would be of interest. Thanks, Frank [1] after "my network, my rules"