I store kegs empty and sanitized under pressure. I normally clean three at a time and push the iodophor from keg to keg. Iodine looses its effectiveness pretty quick when mixed to working strength and it's also pretty cheap if you buy the liter sized bottle.
I disagree with half filing the keg. Fill it up and push out the sanitizer. Clean, sanitized, purged and pressurized = easy kegging.