I have used one for over 60 shots before, just to see how long it would last. The plastic was all washed out, and the blowback was horrendous, but it would still have worked. I really don't like the primer carriers, and haven't used them in years. I have several custom breech plugs that use a bare 209 primer with no blowback.
The blowback starts with the first shot and progressively gets worse with each additional shot. The company stated 20 shots per carrier, they will do it, but not well.
On the other hand, I have had some only last just one shot. I shot a 3 shot group with 80 grains of Black Mag'3 and a 430 grain lead conical and blew all three primers, locking themselves in the carrier and splitting the plastic.