Talisman of Purification stops working late game?

So I was building Talisman of Purification for a few matches then at first I thought it was a bug or maybe I was only allowed to use it once or only use it early game, but when reading the item it said nothing about that it just said what it did but didn't tell me if it was a one time use or only a early game use? Sorry if it's a dumb question but it's just got me thinking if it's a one time use is it worth it to actually buy the item?