Hi Yujai and welcome

I probably wouldn't let him skip the afternoon nap too many days in a row... he may get into an overtired mess, which could start to affect his nights and/or wake up time.
He is already in the transition

. If you see he is continually skipping the afternoon nap, you can try the other option/shorter am/longer pm nap and wake him up 45mins into the morning nap so that he sleeps longer in the afternoon and bedtime is still at a decent hour. Or you could let him sleep up to 1.5hrs and maybe he just needs a little more A before the afternoon nap (try 3.5hrs to start with) and not let him sleep longer than 45mins to preserve bedtime.
During the transition period, babies often have longer days so you may not always be able to have him asleep by his usual bedtime, in the case where his afternoon nap started later than usual
Don't be in a hurry to push him towards 1 nap as he may not be ready for that just yet and you may have to continue to regulate his daytime sleep/wake him from naps, etc... until he is really ready for 4.5-5hrs A, which may take a couple of months. Some babies do the transition in a matter of days/weeks but others take longer...
You may also have days where he sleeps past his usual wake up time and if that is the case, I would aim for 1 nap day, around 4hrs from the time he wakes up and let him sleep as long as he wants (don't wake him).
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How is everyone else going? We've had some shocking days lately. She's sick again (I can see 2 bottom teeth coming through) and I let her sleep yesterday without waking so she had a 2hr morning nap and another 1.5 in the pm and was awake crying at 5.15am. I fed her and she went back to sleep till 7am. Today though we had to go out and she fell asleep for 10mins in the car at around 10am and I put her down at 12.30pm in the afternoon and she only slept 45mins. She was so exhausted by bedtime. I put her down at 5.30 (that's the earliest I could do) and we've already had an OT wake up just now and I had to pat her to sleep. I think she'll wake early again tomorrow. She's been doing so well sleeping through, I really hate these early wake ups and I don't like feeding her back to sleep but I know nothing else will work! I just hope that once we're on one nap, she won't need it anymore. It's not everyday but when it does happen, I worry it will be a prop!
I am back at work on Monday

. I am so sad about leaving her... I just hope mum sticks to my routine, which has been working relatively well (except when she gets sick!)