Why did Gandalf allow Bilbo to keep the ring for so long?

He didnt know it was the one ring till frodo was about 50(in the books) he had some suspisions but saruman fooled him saying it was lost forever in a meeting of the white council and he let the matter be when bilbo just gets the ring thinking it was one of the lesser rings, only when bilbo got fucked up in the head when he tried to leave the ring behind before going to rivendell did gandalf start to have suspisions again and started to investigate, it took him about 17 years to learn the truth.

First, the Ring did not affect Bilbo as quickly or as much as it did, say, Gollum. Second, Gandalf didn't know it was the Obe Ring until his talk with Frodo.

Gandalf did know very well that the ring Bilbo had was the One Ring. However, he did not take it himself because in the end, not even he would have the strength to withstand its power. Gandalf could not have immediately sent the ring to be destroyed because of many obvious dangers along the way. I think that he did know how to destroy it though.

Because, 'clearly the love of the halflings weed had slowed his mind.' Hahaha! :P

To keep it out of the wrong hands.