I can make my way up to a DOUBLE C on most days, but I find that sometimes I just can't do it, even after only a few seconds after I just did it

Like, I'll play up to a G (octave above staff) fine, put down the horn for 30 seconds, pick it up again, and not be able to do it. Is it normal for that to happen, anyone else experience this? just an airy sound with a squeaky/airy tone.
I am using a Yamaha 11B4 mouthpiece, jaw slightly forward, tongue arched to make an "eee" sound, very little pressure on the mouthpiece, tight corners, same settings every time.