Hi!! Sleep consultant here!!! Naps will be short 30-45min. A 4 months will try every 1.5 hours. Sleeping less during the day doesn't make babies sleep longer in fact they are overtired and wake up more often!!!! Stick to a good schedule and this will pass fast! 🥰❤️
I don’t think nap length depends on whether your are in regression or not. You should be following age appropriate wake windows and their last nap be a catnap capped at max 45 minutes.