Extra day at end of RS Central Europe (fka Eastern Europe) Tour?

Extra time in Ljubljana would definitely be worth it, IMHO. It's a pretty, very walkable city that is worth some extra time. You could also take a day trip or two to see more of the surrounding area, which is filled with interesting sights and beauty. I was there on the Adriatic tour and it was a highlight of the trip.

We just did the Central Europe tour last month, and we spent an extra two nights in Ljubljana at the end. Definitely worthwhile -- it's a wonderful small city with a fun cafe/restaurant scene along the river. We took a day trip to Postonja Caves and Predjama Castle on Monday...absolutely amazing and we highly recommend it. We booked it with a tour company and it was about an hour away from Ljubljana.

I took the Eastern (now Central) Europe tour two years ago and it was great!
However I may be an outlier, but I didn’t feel the need to spend any extra time in Ljubljana. Don’t get me wrong, it was a cute, small-ish city, but the afternoon we spent there on the tour was enough for us. Not sure what we would have done with an extra day there. There aren’t really a lot of sights, but probably if you like relaxing at cafes, etc, it would be a good fit. Not necessarily a bad thing after such an active and amazing tour:)