Got notice this morning that Apple Watch has 10.0.1 update available. It does say it is the largest update ever but having my watch on the charger and my iPhone next to it for the next 20 hours is not acceptable. I hope it can be done in steps over the next couple of days.

Ummmm, what? 20 hours? The hell you talking about?

Sorry to tell you this but it is not the update.

Either you have bandwidth issues, or you have phone/watch issues.

I updated two yesterday.

The long part was updating the phone first.

Be sure your phone is up to date before you try to update the watch.

There are troubleshooting methods depending on the version of the phone and watch.

As others noted it is your wifi speed, not the update. The estimated time is dynamic and changes as progress is made.

Mine started with a 10 hour estimate while on guest wifi at a hotel, but within minutes ticked down to a 26 minute estimate, and was done in less than 20 minutes.

My first Apple Watch, a Series 1, Gen. 2, was slow to update, but, nowhere near that slow. IIRC, it'd take an hour or so for a major WatchOS upgrade. Something is awry here.

I just applied the last set up updates to my iPhone, iPad, and Apple Watch. I didn't watch/time it (I think I went and took my shower while it was updating), but, I don't think it took more than a half-hour or so? That was for WatchOS v. 9.6.3.

And, no: Updates/upgrades can't be done in "steps." Has to be done all in one go.

I guess it is time to replace the old Apple Airport! I have been suspecting it for a while but been putting it off. I did like the auto recovery features that it had but cannot delay any longer.

Mine took about 2 hours to update yesterday. The phone was already up to date when I started.