I will usually leave empty kegs until I have 4 or 5 to clean at the same time. Then I rinse them to get the loose stuff out, and heat water up to about 185. About 1/2 cup of PBW in the first keg will clean it just fine within 20 or 30 minutes, then I use a jumper hose to pump it to the next keg, and continue until they are all clean. I rinse each keg as it's cleaned, and once they all are clean I pump about 1/2 keg of nearly boiling water through the jumper from one keg to the next. Turn them upside down to dry overnight then put the clean lids back on. In 16 years of kegging I've never stripped one down after the initial teardown/cleanup. OTOH I know people who completely disassemble their kegs after each use.