As long as you're changing the babies diaper often enough during the day and not letting the baby stay in a wet or dirty diaper longer than 3 hours then there's no need to apply diaper rash cream every time you change the kids diaper.
I only used diaper rash cream on my babies when I changed their diaper for the night which meant that the baby would be not getting a diaper change for around 8 to 12 hours depending on how long they slept for.
That meant that they would be in wet and possibly pooped in diapers overnight so I used diaper rash cream during those times.
I never really used diaper rash cream during the day when my kids were in diapers because I changed them every 2 to 3 hours which kept there skin dry.
Disposable diapers are very absorbent and usually the baby is unable to feel any wetness on their skin because the diaper is holding the wetness away from their skin.
But during the night or when on a road trip where I wouldn't be able to change their diaper often enough I would apply some diaper rash cream to their diaper area.
My kids never had a diaper rash because I kept them clean and in fresh diapers often enough and only needed to use diaper rash cream at night as a preventative measure.