Not sure you can......it's not that he isn't doing well with those 13h nights, that's a good amount of sleep I agree, it's just that the 11h A time is totally exhausting for them and several days of that in a row leads to OT whatever you do. You can do an earlier bedtime still although I know you're not keen on that but tbh we didn't go earlier than 6.30pm once NNDs became quite frequent. All you can do is try to muddle through for now and accept some OT is inevitable. If he won't nap, you can't make him in which case EBT is your friend, and keep offering the opportunity for a nap if it looks like he might go x