Mine are reused by colour.
If I'm washing ~say~ a load of purples, I throw in all the purple Colour Catchers plus one unused one. If the new one comes out white/ultra light, the load goes into the dryer; if I can't tell which Catcher is the new one, I'll add another unused Catcher and rewash the load.
I've noticed that as I acquire more Catchers in a particular colour family, they get darker, and I rarely have to do a second wash as all of them are absorbing dye.
So IMO they do keep absorbing colour almost indefinitely: some of my Catchers are at least five years old.
*LOL* The various stacks of colours next to the Tide are "Art".