Q:

If it's too early to award a bounty, indicate so earlier

When I click on the Bounty icon to award it, I get asked Are you sure, and then I say I am sure, only to be told that it's too early.

Just for kicks, here's the sequence in pictures:

I see my bounty is still outstanding and that I have a great, spot-on, bounty-worthy answer:

I decide that I don't want to to forget to award this bounty to a deserving user:

I see that I need to hold that thought for another two hours:

What's worse, is that I did the same thing 3 hours ago.  The only way I know that I can't award the bounty yet is to try (and fail) to award it.  (I guess I could notice on step #1 that the bounty doesn't end for another 6 days and infer that I still need to wait until it ticks over to 5 days.  But I wouldn't want to call that solution intuitive.)

A:

The simplest solution is to make the link grayed out with hover text that explains the bounty has not aged past the waiting period. A slightly more sophisticated solution would involve a countdown timer and a link to the appropriate FAQ. But I'd be happy with the text of the dialog box be replaced with You may award your bounty in 6 hours.  No need to scare the user until the threat has some teeth.  
(It's a really bad dialog box text anyway.  Since the action is irrevocable the box is needed, but the "THIS ACTION CANNOT BE UNDONE!" is obnoxious and too scary.  Most people don't read the text of a dialog box anyway.)

A:

Probably best to have a message viewable to the bounty-setter only under the bounty notice: "You can award the bounty in X hours/days" and completely get rid of the "+XXX" buttons next to the posts until those buttons are usable.
Don't gray them out - just get rid of them until they actually do something.

A:

This feature has been implemented. When you add a bounty to a question, the button for awarding the bounty to an answer is now grayed out for 24 hours, with an appropriate tooltip message and cursor.
If anyone wants to see how it looks, I encourage you to add a bounty to this question.
As others can't try, since I just did, I'll post a picture to comfort them: 

