Hello and welcome to BW forums
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Let me see if I can answer some of those questions for you.
1) is a 4hr easy too much for his age?
Maybe. As you have said there was some sleep disturbance for his naps he could well have been ready for a longer A time but possibly not quite ready for a full 4hr EASY. Some LOs do well on 3.5hr EASY for a time, there's an example here you might want to look at:
Time to Transition - 3hr, 3.5hr or 4hr EASYIf you scroll down you'll see the 3.5hr EASY sample, remember it is not a strict routine, just guidance and you adapt for your LO.
Also some LOs are ready for a longer A time but not ready for a longer stretch between their E times. Tracy said some babies do not reach the 4hrly E until a little later but that most would be able to move to 4hrly E at 6 months. My own DS stayed on 3hr E although his A times stretched and were longer than guidance times.
So, to answer your question it's really about looking at your own LO and seeing what he is ready for. EASY is always about the individual baby you have rather than a one size fits all schedule. Some LOs are ready to switch their routine earlier than others.
2) can his day naps rob him of night sleep?
It could but unlikely unless he is sleeping a huge amount in the day.
As you are in the middle of a change in routine you might want to see how things pan out for a few days but perhaps then you might like to post your (real day) EASY times here and we can have a look for you?
3) does anyone ever do EASA before the next feed?
Yes. If LO is not hungry and if the E time is not due when S finishes then it's fine to have some A time between S and E. The idea of EAS is to separate eating from sleeping so that there is less chance of a feed-to-sleep prop, it doesn't mean that you must automatically feed LO as soon as he wakes. If he's hungry though I would go ahead and feed him even if the E time has not fully passed (so if you are aiming for 4hrs and he is hungry at 3.5hrs for some feeds that's okay, if he appears hungry but then takes a tiny amount then chances are he wasn't really hungry but something else, in that case you can be more confident he will feed better on the longer E time).
4) for night time waking, should I apply the same settling as a nap waking and for how long?
I am having trouble fully knowing if baby is waking at night out of hunger or starting habit (sometimes takes full feed other times not). Do you think it can take my milk some time to adjust to redistributing for the new schedule (dropping a feed) and baby is hungry at night?
Is he an independent sleeper usually? So you put him down awake or drowsy and he settles himself to sleep?
Increased night feeds can be to increase your supply and can also be a grown spurt, either way he needs a feed. If he is more hungry at night due to dropped day feeds I would suggest reducing the E time in the day to get him that extra feed back in, if all his feeds are full/proper feeds in the day then he is unlikely ready to drop one. I wouldn't worry yet about night time habits, if he is sleeping in his own cot and wakes a couple of times for food that's perfect
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If he wakes and say only an hour has gone by since he last ate that's when I'd suggest trying to resettle without feeding as he is unlikely to be hungry.
5) not sure if this is related but he's been sucking on his hands like crazy
He might have some tooth movement, some LOs can start teething as early as 3 months. Otherwise reasons for sucking hands may be to self sooth, hunger, or acid reflux or just enjoying and exploring bits of his body that he just discovered he can control and touch. You'd probably need to do some investigating to find out which but if he seems healthy and happy and you offer a feed and he doesn't want it or doesn't take a full one then you can rest assured it isn't hunger.
I tend to get stuck to a certain schedule... Not sure how to be more flexible if needed (I.e. Some shorter/longer naps, activity time, etc..).
In general once you have a routine that works for you and LO you can count on it for a while, that's why many of us like EASY, it makes the day more predictable. Your EASY may not look like my EASY but it will still be predictable for you and your LO. When you have that the only tweaks that you would usually make would be for instance if you had a one-off family commitment or something and LO missed a nap or had lots more stimulation than usual or only slept a short nap because you were out so might need a slightly shorter A time and earlier nap to help with the tiredness.
I wanted to get suggestions early in the event I should change something sooner than later. Also wondering how long people would ride out the new change to see how it settles before changing things up.
You said you started this week but I don't know how many days you already did. If you feel things are not going the right way I would think about stepping back to perhaps the 3.5hr EASY or to look over your EASY records (if you have any) and observations and see does he need the longer A time but the shorter E time. Not every A and E time have to be equal throughout the day either. You might find a perfect routine where the first A is longer/shorter than the others, and that's fine too.
For what it's worth this is a time when many LOs go a bit off track in the routine, naps often go short, we see it a lot, happened to my DS too (at 3.5 months, it's more commonly known as the 4 month regression) so you are not alone if you get short naps for a while...at the same time I do think it is worth trying changes to the routine just as you have done to see if the longer naps and a more settled routine can be restored.
I hope this has helped a bit rather than confused you further. If anything is not clear please let us know.