When will my baby nap longer

My baby is almost 7 months.

All the “books” say he should be taking 1-1.5 naps yet he takes 35-45 min naps. And I know he needs longer ones because his night sleep is being affected by waking up at 5am now.

When he gets solid sleep during the day (we will get a burst of 3-4 days of him taking great naps) he sleeps amazing and wakes up at 6-6:20. Yet I don’t know what is different. We watch his wake windows and cues, he naps in the same place around the same time (crib nap) yet some days I’m like I nailed it, he fell asleep so quickly, yet will wake up 35 mins later.

I’m tired of reading the research of “he’s overtired” “hes not tired enough” because we’ve tried it all.

Just curious if this is developmental? I feel like by now he should be napping longer.