absolutely keep them.
Even if they're slightly worn, they'll still be good enough for chasing threads.
First time you use one to clean out an old rusty or greasy/grimy threaded hole you'll wonder how you've lived so long without them.
Get the dies to do external threads and you'll be even happier.
Seriously - clean threads are a pleasure to re-assemble and Soooo worth the little extra effort of cleaning them out properly.
Remember the one most important rule with taps: treat them like they're made out of glass.
They are very brittle, and snapping one in the wrong place will make you miserable.