Okay, I just responded to your other thread. If you read my post there, this is the same one, but I'll post again because who knows what comes up in the 'search' section a year from now, lol.
We just got back from an 8 day that we booked 2 months before sailing. We were down for the 5:30 seating, but somehow got changed to "my time" dining, which starts at 6:45, I think. We were eventually accommodated on the 5:30 seating, which was our preference, but if you want 'my time' it didn't seem to be a problem. We did see line ups of people on our way out of our seating, but I don't know if they were all hoping for a table or if they'd made reservations earlier. Also, when we were still in flux about our dining time, we were told to come at 5:45 and they'd fit us in, so it did seem like they were flexible about their dining times.
You can buy the packages on board, but if you have the time to wait for sales before your sailing, do that. We got ours during the Black Friday sale. Same with our internet packages. They were cheaper than getting them on board.
We found lounge chairs on deck were commandeered by people with towels and towel pins holding them there. There were many empty chairs, but very rarely was there one without a towel and certainly not in a prime space. That was a real pet peeve of ours, but I think it's a problem that crosses all lines.
Our sailing (Odyssey) was showing "The Book". We got tickets for that as soon as we were able. It books up quickly. That said, I think you can walk in after a certain point without tickets. So if you have tickets, get there early enough to claim your spot... and earlier than the ship staff recommends. They never told us the right information.
There were other shows every night, but in another theatre. We didn't go to all of them, but again, if you can get there early, you'll get the better seats.
I didn't use our in-room TV, but I was on deck later in the evening a couple of times and there was a movie showing on deck (once it was Ariel... go figure!). On the Odyssey, the adult section is open all night, but the pool shuts down at 8pm and the hot tub stops 'bubbling' at midnight. We liked going for an 11pm soak. It was quiet at that time.
One other thing, since you said it was an 8-day. Ours had 2 formal nights. Day 2 and 6. Not sure if that would be true for all 8-day sailings, but it's something to think about if you're into that or want the photos and the photo packages.