30 to 45 min is pretty fucking awesome! That's some dedication/ I think the longest for me has been about 15min. I haven't experienced what you're writing about, I hope I never do.
Maybe it's just a one time thing or a natural reaction of tired muscles. Maybe you just need to suck more cock to build strength?
I'm going to be back in WA for a few days, sometime around the 2nd or 3rd week of Aug.
You are welcome to practice on me, but I'm sure I won't last that long. 😀
Where in Seattle are you?
You are welcome to DM me on https://community.cockworshipper.com