not sending a reminder

An opponent has advised he/she will be away, a reminder has
appeared on my games list which I do not intend to send as I know
he/she will make a move upon their return.
My question - if a reminder is never sent - what happens to the
game ?

Sending or not sending a reminder has no bearing on the game.
When the time out period has been reached, another icon will appear
allowing you to claim a victory. If you do not claim a victory, nothing
will happen and when your opponent returns it will be their move.

Hope this was helpful...
Marc