Mine are 3 yrs 9 months apart so now have just over 3 year old and very nearly 7 year old.
We do bath time together unless older one has shower bit later or is at football practise then they both come downstairs for a drink, little one goes up about 7 ish and older one goes up45 mins later. We’ve always done the split since LO dropped nap. 12 hour day very common sometimes 11.5 hour if very tired and won’t nap, but yes every say 4 days we’d get a little 20 min CN but I always prefer no nap as BT and night sleep better.