My 12 week old has predominantly 30-40 min naps, we have been getting the odd one over an hour in more recently. We have been going by his awake time and cues, and have been putting him down for an evening nap anytime from 5-6PM (as long as he is up by 7PM). Are we sabotaging his night sleep. Sometimes I think it doesn't affect it at all - maybe that is on days when he hasnt slept much earlier in the day.
We are starting his bedtime routine a bit earlier now at around 7:15, but his last feed can take anywhere from 30 mins to an hour, so his actual bedtime varies and is usually between 8-9.
He didn't seem tired at bedtime last night, he had a nap at 515-545. And he seemed happy and chilled through the change after bathtime (when he normally screams)... We started his bedtime routine at 7:15, fed at 725. But I struggled for half an hour to get him down at 8, so he went to bed around 8:40. I just put him down awake to see what would happen and he did fall asleep, he was just fighting me beforehand.
He also had a long nap yesterday (1hr and a half), this hasn't happened for a few days.