very poor reasons
all a shutdown does is clear out your buffer cache and shared pool making the database have to work hard when you restart it.
What does keeping the archive logs have to do with anything. Don't you keep all of them anyway?
Well, the only reason I would do colds is that the database is shut nicely and do not have to keep the archivelogs produced during the backup... also, shutting down the database once in a while avoids having problems with the fragmentation of the shared pool and stuff like that...
