We keep separate PLNs and BLKs for each version in the sketch phase like jobNo_SK-01a, where SK stands for a sketch. BLKs have similar numbering but they don't have to necessarily follow the numbering of PLNs as the book can include several variations issued under only one Option-01. So typically we have PLN files, lets say, 05104_SK01a, 05104_SK01b, 05104_SK-02a but only one book 05104_OPT-01a that includes links to all the PLNs. And we store all books and PLNs in the superseded folder. PDFs/DWGs get stored (a hardcopy as well) only in case of exporting/sending them to consultant/client for a reference (and liability reasons)
DA (Development Application) phase is using completely different template and naming (it's the same with CC/Tender/CD) so we virtually draw the bottom line after every phase of a project documentation. But it's usually one PLN/BLK file business (either solo or teamwork one).
Some links with ideas:
http://archicad-talk.graphisoft.com/viewtopic.php?p=32386&highlight=revision#32386
http://archicad-talk.graphisoft.com/viewtopic.php?t=5490&postdays=0&postorder=asc&highlight=revision...
http://archicad-talk.graphisoft.com/viewtopic.php?p=17281&highlight=#17281
::rk