is 8 days too long in Nafplio

I think you have a good plan using Nafplio as a base for an extended time.There are many excellent day trips to take from Napflio.

Napflio is lovely, but "day trips" really means a lot of local windy-road driving in the Peleponnese. Olympia for example is about a 3 hour drive west, and then three hours back. On the other hand Mycenae and Epidavros are easily reached from Napflio, and can be done together in one day. Only you can decide how much driving is too much, and what sights you want to see. Maybe picking two 4 night stays including Napflio and a western Peleponnese town would be more driving friendly.

I think it depends what you want to do. I agree that if you want to be sight seeing most days, then you are going to be driving a lot. If you want to hang out in town and just be there at least some of your days, then Nafplio is a very pleasant town.

If you want to sight see most days, I would look at spending half your time somewhere else. You might look at Pylos as it is well located for day trips and would be worth staying for 3 or 4 nights. Gythio is another possibility although I don’t think the town itself has as much to see as Pylos. It is, however, in close proximity to other sights you might enjoy.

I also agree that 8 days in Nafplio will be too much.

Not only for the reasons mentioned above, but also because you'll quickly get tired of returning to Nafplio every evening after the third day. The old town is small and only has about 150 permanent residents. Plus the temporary residents who work in hotels, restaurants, and tourist shops, and there are so many other places to discover in the Peloponnese, as Nick and Beth suggest, another base further west (in Mani) would be a good option.

Nafplio is a lovely, small town with several exceptional day trip possibilities. Pleasant opportunities for strolling and dining along the coast. Honestly though 8 days days seems to me like an a long time. I’m trying to get into the notion of slow travel but that would be very slow. However, I can say without reservation that our stay at the Hotel,Aetoma was among the best of any, anywhere over many years. Spacious room with balcony, charming, accommodating host and a large beautiful breakfast. We took the bus to and from Athens, but I think they offer parking facilities Safe travels.

Hydra might be an option for a couple of relaxing days. I believe it’s quite a short ferry ride from Nafplio to Hydra. We visited both on the Rick Steve’s Greece tour and really enjoyed them both.