According to what I've read Bitcoin is limited to 21 million Bitcoins, so if your question refers to when will there be a stop to the flow of Bitcoins via mining it will stop once 21 million have been mined.
It will not stop because after the 21 million will all be mined, those transactions will still be mined for it to be processed. Miners will still be earning through those fees sent by millions of bitcoin users. I doubt btc will run out. its not like we will all leave a bit of btc on every unused wallet.