Any tips for thumbs players?

I am a thumb player and have been playing bandori for around 2 or 3 years, during those years I have been playing with thumbs and also developing some "strategies" to help me play some songs because of its difficulties.

Lately I have been having some problems with songs in Expert related to endurance (my thumbs can't move as smoothly in the end of the song as in the beginning), the solution that I have for it is my position and that helps me solve this endurance problem but also forces me to play in only one way when playing difficult levels so I wanted to know if someone knows some other ways to help the endurance of your thumbs when playing a song.