There is a little over five inches of unused film at the end of a roll of Tri-X.

I have an old roll of film that I screwed up and spoiled but, instead of throwing it out, I saved it for practice. Times just like these.
I just wind it back to the beginning again and use it over and over. Since it has already been exposed to light, it doesn't matter.

Anyhow, I loaded the practice roll and traced around the opening in the film back with a pencil to mark every frame.
Everything works the way it's supposed to but, when you get to the eighth frame, there is enough film left over to make one more exposure, plus a good inch of film left at the tail. That includes a generous amount for inter-frame spacing.

Yes, you have to load the roll correctly and you have to wind carefully at the end.

I figure this is like the 37th shot on a roll of 35mm film.
It's there. It's usable film but you can't always count on it. Proceed with the understanding that it might not always work.