I believe you are on step 2.
By sending the reminder, you're letting the high bidder know that you're willing to go by the TOS (terms of sale) that eBay has established. I think that this translates that you're following eBay's rules and if they don't repond once the reminder is served that you will be following through with the NPB (non paying bidder) alert. This lets the bidder know, you're not going to play "THEIR" game.
If they do not pay after the reminder letter is send, you need to follow through to request your listing fees back.
Following through with this step makes the bidder accountable. 3 strikes and they are OUT! Feedback itself means nothing, but if 3 people (whether buyers or sellers) say that this person did not follow through with their bid or sale, then this person will be suspended from eBay indefinitely.
Sending the reminder scares some people into contacting the buyer/seller right away. If payment has been sent, this will get their attention to inform you of that fact!
There are some bidders who suffer from what is termed " buyers remorse", these people may never contact you, and may never pay. If you encounter one of them (I'd say no contact of any form in 10 days) then I would go ahead and file for a NPB (non paying bidder) form to collect my listing fees and go from there.
It's in eBay's TOS (terms of sale) that if there is no payment or communication (or 10 days used to be the limit anyway) then you could file the NPB and be well within your rights. You DON'T have to wait forever!
If after this point the seller is willing to pay, you can play the game by ear. Let the chips fall where they may if you will. If you're in the position and wish to sell at that time, by all means sell. If however you've resold your item......TOO BAD!! You're now calling the shots and can do as you please.
I can't stress enough however how important it is to make sure you file that NBP form! You collect your fees back, but at the same time, you add one strike against that buyer or seller into getting them pushed off eBay.
Of course we all know they can sign up with another name, but even at that, how many credit cards do you have before you run out for registration purposes?