Cinque Terre

It depends on what you want to do. You could easily spend a week if you just want to relax and do some hiking. Or you could hit one of the cities for a quick look, take a few pictures, and on to the next place.

We stayed 2 nights our 1st trip and are returning for 2 nights this trip - enough time to hike or take train and explore the villages - if you want to do beach relaxing as well, you may want 3 days.

Xinwei, The answer will depend on what you want to do there (ie: hiking, exploring the area, relaxing) and how much time you have available. If you just want a brief look at the area, two full days should be adequate. However, you may find after you arrive there that you wish you had booked more time. Have you decided yet which of the five towns you'd prefer to stay in? For travel in May, I would suggest getting a room booked SOON!!! Happy travels!

in general 2 days is good if you want to do a lot of hiking you can stay longer or if you like to relax in one place you could stay longer
I think it's pretty common to spend 2-3 nights

My daughter and I stayed 3 or 4 nights last October. The weather was gorgeous. First trip to Italy. We needed to decompress after our long trip over and a terrific 5 days in Rome, so the time in CT went fast. We did some hiking, but also just hung out at the beach or explored Monterosso, where we stayed. Lots of cool discoveries in that little town. Go up into the hills! All our other time was in cities (Venice, Rome, Florence) so 3.5 days was not too much in CT for us. We like to camp and hike, so getting out of the city for awhile was a relief.
Enjoy!

We stayed in Sestri Levante instead of right in CT and it was FANTASTIC! no regrets - had a great time!

Thanks for all your replies! Is there any good and affordable B & B to recommend? Thanks