Unsafe brass
Grizz--.303 Lee-Enfields are notorious for stretching brass, due to their single bolt lug, 'way at the back of the bolt. Most people who reload for them are aware of the problem and only neck-size the cases (or shoulder-bump if necessary). And .303 brass is rare enough that any reloader who shoots it will take it home with him--you'll never see it at the range.
Other than that, there's this technique called "case inspection," that you use to see if the brass has been unduly distorted before you picked it up. You know, things like looking for split necks, odd-shaped bulges, flattened primers, shiny spots on the bases, stretch rings just above the base, loose primer pockets, etc.
Honest, Grizz, I think you're being excessively cautions, and this from one who usually advises caution, moderation, go slow, walk before you run, read up on it before trying, etc, etc.
Caz is correct--Most target pistol shooters re-use whatever brass they can lay their hands on until it splits. Some brag that they wear the headstamps off the cases, running them through their progressive reloaders. Serious target pistol shooters run through multiple thousands of rounds per year. If they all had to go on yr reccommendation to use only once-fired brass, all but the sponsored shooters would be broke!
Rifle brass needs more care, but here, too, there is much saving of $$ to be had by re-using brass, and the more you shoot the more saving. I don't know of ANY shooters who reload, who re-use rifle brass just once and then toss it.
Now, having said all that, I'll add that if using each case a total of 2 times then tossing it, is what makes you happy, and you can afford it, go for it, man! It's a hobby, not a religion. There is no dogma. But I don't think it's good advice to hand out generally.
