I'm using a 3rd party 20W adapter, which I've had for about a year and the Apple charging puck that came with the Series 7. Ever since I had my first watch (s4) my routine has been to charge for about an hour at night before bed, and then top it up to 100% again with another 20-30 minutes on the charger in the morning when I'm getting ready. That's worked fine for years.
Since updating to WatchOS 9 I've had some unusually slow charging activity on the Series 7. It's taken up to an hour and a half to reach a full charge before bed from a charge of 50-55%. On WatchOS 8, 45-60 minutes was sufficient.
In the mornings, well let's take this morning as a good example. When I woke up, the watch was at 92%. I put it on the charger at 5:30am. At 6:00am I checked it, and it was at 94%. I didn't have to leave the house yet, so I let it keep charging another 30 minutes and it got up to 96% before I had to leave. That's ridiculously slow.