Nights didn't lengthen here until after DS settled into the no nap routine. I think at the time I was happy with 11 to 11.5hr nights, he lengthened to 12hrs which he is still doing at 4.5yo!
Many people recommend shorter days but IME this risks EW and then the need for a nap to get through the following day. If nights are 11.5 I'd go for 12 - 12.5hr day.
If you do naps too often the night may not lengthen and the it may take longer to settle into the routine. DS had a few little naps in the car here and there where it couldn’t be avoided and after 2 weeks I could see we were both shattered, yk the behaviour was difficult, by this point there was no chance he would have gone for a nap in his bed but he said yes when I invited him for a nap and cuddle with me in bed. We slept on and off for 2hrs - but that was the last real nap. Following that just the odd micro nap in the car when he was lulled by the movement. I very quickly learned he didn't like to be left to sleep longer in the car it made him dopey and grouchy.
At some point I also worked out he could do a longer night a couple of days per week which meant a weekend lie in!!! I just moved his morning timer lights 30 min later and told him to have a lie in. Worked great and I enjoyed it while it lasted.
