The number of times a particular trap can catch prey is variable. Some blacken and die after the first bug - others can catch several, although 3 or 4 seems to be the usual maximum. The traps also die off naturally after a couple of months.
With a health plant, more traps will grow and mature, so older ones dying off is no big deal.
By the way, if you trigger a trap, or it partly closes in an unsuccessful capture event - it uses up one of that trap's "lives".
