You'll know when you need these days. It'll be when you get up before your alarm goes off and you arise feeling great. It's a beautiful morning and you think "There's no way I can go to work today, theres too much I'd rather be doing". So you make the call. "Hey boss, I'm not coming in today, I feel way too fucking good, see ya tomorrow"... Maybe. But these days will not be for sitting around doing nothing. You will be required to bring in documentation of how you spent your "well day". Like a huge bar tab or pictures of you doing something productive.
In the new world, we'll have equal numbers of well days as we do sick days.
AND SO IT SHALL BE WRITTEN!