How does Gamefly returning games work close to membership end date?

I have two games out with gamefly and my membership re-bills in 6 days.

I no longer wish to continue membership, but would like to play the games as long as possible.

How does this all work?

To cancel my membership do I have to have all games returned?

I don't want to get stuck in a situation where the games are still in transit back to gamefly, but the re-bill date passes and they charge me for another month.

If you cancel your membership now you still got 6 days left to keep the games. 

I usually call on the final day and tell them I dropped it off in the mail so they can note your account.

From Gamefly's Term of Use:

As a member of the subscription service, you agree and authorize us to charge your Card for the current retail price or replacement price (whichever is higher) of a game (an “Unreturned Game”) under the following circumstances:

• If we do not receive a game within seven (7) days of cancellation or other termination of your free trial or paid membership, unless you can document that the game has been received by GameFly by using shipping with a tracking method;

As long as you get the game back to them within 7 days, you should be fine. I'd give yourself a few days cushion though.