Purgeable REGAPPs are just strings, so even a few hundred won't bulk up a drawing too much. A few thousand gets to the point of annoyance. But its a good idea to pull them anyways, if only to keep them from propagating into other drawings.
One of the Engineers we work with a lot has been sending us drawings lately that have 100,000+ regapps in them. Purging takes files down from 3.5MB to more like 800KB. The drawings also take a while to open.
I told him about purging regapps, and he was pretty happy. He didn't know anything about them, and he likes to copy-and-paste between drawings, so he had infested most of his DWG files with hundreds of thousands of regapps in each. He said, "It seemed like I had a lot of really large files lately..."
