When can I stop putting diaper rash cream at night? Does it only stop when they are potty trained?

If you're talking about medicated creams like Desitin, we only ever applied it once when he had a diaper rash - and stopped after that! Never had to use it again thankfully :) If you're talking about normal baby lotion, we stopped applying it regularly after a year or so - now only applying when there's redness!