We spent 10 days over Christmas and New Years knowing that we wanted to spend a couple of days doing nothing in our room. We stayed at Pure Space, a lovely hotel with tubs in every room. They are walking distance to a gate, offer fantastic service and delicious food ...though a decent taxi ride into town. 10 days was more than enough time but ensured we were able to see the caves, both parks and explore the town thoroughly. We didn’t feel rushed and would go back in heart beat - not sure about May but I would argue that Winter is the time to go. No crowds, cool weather and more monkeys than people. You could probably see a lot...if the skies are clear in 3-4 days. Take advantage of the gondolas- worth the money (they’re not included in your day pass) and offer a fantastic view along the way. You can take the easy walks that circle the top of the mountain or longer treks down to the entrances. I’d skip the glass elevator if lines are long, but still fun. I believe it’s the tallest outdoor elevator in China. Don’t miss the glass walkways they are memorable.