Supposedly you can choose to get daily payouts (one transfer per day) or weekly payouts (one transfer per week). Not sure if there are any other options. Most sellers are setting up separate accounts to deal with eBay since once connected to your account they will have the ability to deduce funds if needed for refunds, fees, etc. Supposedly they will take those funds from any funds on account not yet transferred but if not available they will dip into your account. Thus the reason many sellers are setting up separate accounts strictly for dealing with eBay. Many then transfer the funds to their main account once transferred from eBay so that eBay no longer has access. Just food for thought.

Currently no way to issue partial refunds to buyers from what I've heard.