How long can a sale be held unpaid?

[this-is-vinyl]

I have made a sale by auction and I have been in contact with the buyer and agreed that they can pay 2 weeks after the auction ended. Will the sale be cancelled automatically for non payment at a set point or do I have to initiate it? 
If it is cancelled automatically after a number of days, can I request that it isn’t? 
Thanks 

[**peaseblossom**]

You can check at My eBay > Account > Seller Preferences > Preferences for items awaiting payment > Edit

But your dispatch date status will suffer so it would be best to cancel/refund with buyer's agreement and relist nearer the time.