If you just fire it up for only 5 minutes every so often. You are actually creating condensation in the crankcase, since the engine won't be run enough to full heat to burn out the condensation. I'd suggest either let it sit, (I do) or run it for at least 20 minutes at a time..
Nice looking rig.. Did you wax the deck at least ? I do, helps it stay cleaner easier during mow season.
Merry Christmas.