You'll get a notice several days before your token expires, so you can renew it without worrying about a gap, but if for some reason your eBay Token expires before you're able to renew it, don't worry. 

Any orders that happened on eBay, but aren't synced, will sync within 24 hours of the token re-
authorization (only goes back 2 weeks).

 

The only manual work you will have to do is to update any items that may have sold through the Suredone storefront while the token was expired.