It feels like not much is written in stone when it comes to diabetes.
Hi, Lisaopp, yep, that's a fair assessment of it.
Good advice above, and your own thoughts, about having little "iob", active insulin on board", when going to sleep.
But...
There can still be a residual action from fast acting which can last longer than expected.
Also, if your basal, background insulin dosage is too high, that can drop bg quite a lot, but tends to do so slowly. It's worthwhile spending a bit of time doing basal testing. It can be as easy as having a good long lie in on a Saturday until late afternoon - bg should stay more or less the same for the duration, if it goes up or down too much, think about changing the dose. Get your basal right, it makes the rest of it a lot easier, because you're not having to sort out with fast acting insulin what your basal should be doing.
The liver can also be a flighty wee thing. It releases stored glucose to power your energy needs between meals, and your basal takes care of that, but it can also grab back glucose from your bloodstream because it likes to keep stocked up with stored glucose, and that can lead to a hypo too. Which is why some cheese on toast is a good idea after a hypo - putting more carbs in so that the liver can restock without depleting your bg too much.
You have one hormone which reduces bg, insulin, and you now have to inject that. But, you have several hormones which raise bg - adrenalin, glucagon, cortisol, growth hormone - and your endocrine system still makes those.
So, even though it is highly likely you will make a mistake in your insulin dosing decisions at some point - we all do - you've got a whole host of hormones which will still be kicking in there to tell the liver to release glucose to raise your bg again.
It won't always be nice - night hypos can be very unpleasant - but your body will keep you safe.
And there's the cgm angle too - nothing better than your phone ringing to tell you your bg is getting too low at 3am.
Good luck!
