I use sequential numbering as well, but also break it into phases. For instance, if I'm just trying to toss around ideas for myself, I'll go with "Client_S1", "Client_S2", etc. Client name, then "S" for sketch. I'll progress to something to present and call it "Client_P1", _P2, P3, etc. when I get to the preliminary stage, then use F for finals. The way I archive it is I'll actually rename the file and append it with the letter A, so "Client_P2" becomes "Client_P2A". When I open the layout it prompts for the missing file, I attach the current file and it relinks everything. One layout.