I have 100% of the time. I work for myself. What this has resulted in, is that everything I work on, either manifests into something that has a direct consequence on the bottom line. Or I have something that is in progress and I get back to it when I have some inspiration. Or it is something that I can't yet crack and goes into a folder until I pick it up again way down the line.

I know if I recruited for my company. I would have this 20% philosophy.

If I sandbag estimates

I don't even have 0% time.

Not 20%, but I got the manager to give us 2 hours every Friday. I guess that would be 5% time. I was doing C# enterprise work at the time, so I would use those 2 hours on totally different stuff; like brushing up on C++, or dicking around with Perl.

Not formally. However, if I was getting my job done and was productive, I don't think anyone would complain about 20% time. Although my employer is quite flexible and I have unlimited vacation as well, though that is a privilege and not a right, of course.

Yes

Nope. Barely have time to do regular development properly.

Our old CTO used to laugh (somewhat derisively) if anyone asked.

No.

I have 10% time.

I have 5% time. Two hours a week. To work on a project of the company's choosing. They're really proud of that.

If we are hitting targets, yes

Do this in a separate thread.

I have 10%, the Friday at the end of every two-week sprint (today in fact).

Yes

No

Yes

no

Yes.

No

I choose what I work on and no one micromanages me. I have 100% time.