I love going to the Greek mainland. I mostly go to Tolo but I did go to Stoupa for 3 years.
You either love or hate Tolo, we go in Sept and we see the same faces each time. Usually catch up over a beer (or 2). I have met people though who hate it and would never return.
Why do I love it .....it is relaxing, the food is good, the beer is cold and the locals are friendly.
It is a good base to tour historical sites such as Mycenea, Epidavarus, Tyrins (not sure if spellings are correct). There is also Nemea, a wine area, where you can buy nice wine very cheaply. You can also get boat trips to the islands such as Hydra and Spetses.
We usually mix the holiday, some days we sit in a taverna, swim, sunbathe, eat, drink and chat with friends. Other days we are energetic and go off exploring.