Hi!
Just seen this, how did the rest of the day go?
Sounds like the start of the 2-1 transition. So he's not ready for 1 nap but that long am nap is giving you a later, shorter 2nd nap.
Here's a useful link:
From 2 to 1 nap transition (10-12m and older)To answer your specific question about 2nd nap, there is no definite answer, you just need to try different options and see which work best for you, your DS & fits in with rest of family.
9mo is really too young to cope with only 1 nap regularly so I think your options are either:
Do AM nap as long as he wants but then have a later pm nap but cut it shorter e.g. 15-20mins if you think you need to to maintain his usual BT.
Cap Am nap at 2hrs to try to get the CN in still and not have too long a day
Choose one option, try it for about a week. If it's not working, try the other option instead!
It is a messy transition and longer days and shorter nights are inevitable unfortunately,it's just trying to find the least awkward option!