I believe that to fully enjoy the island of Flores and see all its main attractions, you need at least 4-5 days. In that time, you’ll be able not only to visit all the most interesting places by car but also to enrich your stay with hiking.
I recommend doing all the official trails on the island one way, except for PR-04. For this, you’ll need additional transfers, the details of which I’ve included in the description of each hike.
The only thing you won’t be able to fit into 4-5 days is additional and important activities, such as canyoning, exploring the island by boat, or taking a short trip to the neighboring island of Corvo.
If you plan to include all of these in your trip, then 7 days would be the optimal duration for your visit to the island.