Bethpage are my home courses. I play there every weekend. Played the green and yellow last week and both were in good shape for this time of year. Unless you are in crazy good shape, I wouldn’t walk another course on the same day as the black. If you are looking to do 36 on another day, absolutely play the red course in the morning. It’s a long and challenging course and very under rated. Have lunch on the deck overlooking the black course. They have great wings and burgers. I would say an hour and a half in between. Then in the afternoon, I would play the green for fun. It’s shorter and a lot of fun. Lots of birdies to be had. Yellow is an easier option as well. I would stay away from the blue, it’s my least favorite course there.
2 other pieces of advice- you MUST pay at least an hour before for tee time or you will lose your time. Also, on the black, make sure that you are at the starter at least 20-30 min before your time. Second, the driving range is terrible and you cannot hit driver.

The red is opening this weekend and I’m playing it on Saturday and Sunday. Black opens 4/15. Have fun!