This might be a “duh” kinda thing, but I decided to post it anyway. If you’re running out of Airtime, and you aren’t near the ground, simply hit your land key and bring your wings back in. As you get close to the ground, tap glide and you won’t take any damage! I’ve used it a ton when farming Aether.
edit: if you let your time COMPLETELY run out, you actually get 3 seconds of fly time automatically put on as soon as you start falling. Use this wisely!