Is 4 night/days too much for the Cinque Terre?
It depends on what time of year you'll be there and what you enjoy doing.
We just returned from a trip that included 2 nights in Manarola. It wasn't enough--I could happliy have spent 4-5 days there. But we are avid hikers, and also enjoyed the deep-water swimming spots between Manarola and Corniglia.
It really depends on where else you can allocate your time. We, too, spent two nights in Manarola (really, just 1.5 days of activities) and I wish we had been able to spend one more night. But! There's always the next trip! I'm keeping the faith on this one.
We stayed for 3 nights, it was enough for us, we did all the hikes we wanted to do, and all the sites too, we even had time to go swimming and sunbathing, if you are really into hiking you could spend more time, there is so many more trails to explore.
Thank you for your thoughts. We are considering dropping a day and spending the night in Florence before our agritourisimo stay in Tuscany. We will be there in early October and are avid hikers.