I have always found that instead of focusing just on embouchure strength and rest, it is best (for me at least) to focus on having a proper balance between air support and embouchure strength. If the chops are getting tired faster than I think they should, I focus attention to my breath support. After a while it becomes second nature to balance and not fight them. The tone should tell the story. If the sound is very airy, or lacking depth, I try to focus the air better, if it is too "fat" and there is no brilliance to it, maybe put more air into the instrument. I find that for the chops to work properly for me, it is all about the balance.