Sly Gold stack limit?

Brief summary:

Theory crafted Tanklean, build is on reddit if you are interested. But I decided to take it bot lane and experiment with Kleptomancy. With the standard tank build I am able to carry alot of my games. Was doing it top, but was having the issue of bot hard losing which made the build harder. I main support so clearly there was a lot I wasn't doing top lane to help. So I took it bot lane, having great success.

The question:

I go ancient coin and klepto. After about 10 minutes I'm basically unkillable. This allows me to proc klepto as frequently as a lux can proc spell thief. I am getting about 1700 gold with coin and about 600 gold with Klepto. Pretty good for a support generally imo - but I'm nowhere near an expert of course. At first I was thinking full inventories was holding me back with Sly Gold because I was only getting 5 or 6 of them a game - even if the game went 35-40 minutes.

So I decided to leave 1 stack untouched in my inventory to make sure I always had room for it. However in my last two games, I was still only getting 5-6 of the Sly Gold. I'm curious if there is a stack limit? I probably get about 40-50 procs per game on average. Does it become ungettable after a certain amount of collections? Having a tough time finding information on it on the wiki but of course I could just be missing something when I look.

Any thoughts?