The only problem I can think of is leaving out the battery long enough may cause the camera to forget the time. I'm not going to experiment with my K100D to see how long it retains the time.
Many electronic devices have a high value capacitor that retains time while the battery is replaced if you install the replacement battery soon enough. If you leave the battery out too long they forgets the time. Perhaps someone knows from experience?
When my K110D returned from Pentax repair that capability no longer worked. Any time the battery is replaced I have to reset the time. Even a good set of cells replaced quickly will lose the time. It is a minor bug, not worth sending it back for re-repair. Especially since the K110D is used on external power most of the time.
OTOH hand if you are going to store the camera a LONG time then simply re-entering the date is a minor inconvenience. My Eneloops will go dead anyway after a month. But, I never know how long it will be to the next usage so I leave the cells in all the time.