the /savebak command is what you need.

u can stop backups with undomegs 0 ... i do believe :) but that means no undoing :P

/savebak 0: no .BAK files
/savebak 1: only one .BAK file, the most recent one
/savebak 2: multiple .BAK files (default)

Thanks.

The source:

if(savebak==1) formatstring(bakname)("packages/%s.BAK", mapname);
else formatstring(bakname)("packages/%s_%d.BAK", mapname, totalmillis);

Updates I want to read: Saner map versioning using date/time instead of totalmillis (like mapname_%Y-%m-%d_%H.%M.%S.BAK). /savebak 2 could be a good idea for backup fanatics, but actually - using totalmillis - it's pretty annoying to fiddle out what version is what version. I personally use /savebak 1, because having a backup is always a good idea.