Oh yes. I made the mistake of complaining to my wife that she had too many shoes and that she should have to throw away an old pair before she could buy a new pair. Boy did that backfire. She opened my running closet and started counting the pairs of running shoes! I now have what I consider to be a very restrictive limit of no more then 8 pairs of running shoes. :-(
I would add to your collection list, headlamps, socks (lots of socks), power bars, powdered fuel mixtures, sunglasses, first aid kits and of course bikes. I'm at only 3 bikes now, down from four a year ago.
With respect to shirts, 30 doesn't seem unreasonable. I still have my high school cross county shirt. It's on the verge of total decomposition but I save it anyway. One day soon I'll go to look at it and only find a heap of dust.
Humans like to collect things and collecting running gears just shows you're human! Keep it up.