"Thumbs up" to the advice, above!
The more content revisions that are kept on the SEPM, the better the SEPM will be at providing small delta updates to its clients (saving a lot of network bandwidth). The trade-off is that the more content revisions are kept, the more hard drive space is consumed.
If hard drive space is growing short on the SEPM, reduce the number of content revisons kept.
Also, make sure you are using the very latest release of SEP.
Hope this helps!