Oh gosh I have loads of stuff.
Both my horses have 4-5 halters, they each 3-4 coolers and blankets, I have 3 full sets of boots for trailering, i have a huge range of protective leg gear for riding, i have 2 saddles, loads of bridles, at leat a dozen saddle pads, lunge whips, crops, lunge lines etc etc etc...
Over time all the horses I have owned have required different sizes of gear and tack and since I take good care of my stuff I still have all of it.
You should always have duplicates of most pieces of tack. You can always use them.