Not sure about this. 20% time put some boundaries, and marks that you should be doing something different. It can be typically abused (hey, I'm supposed to have

Not sure about this. 20% time put some boundaries, and marks that you should be doing something different. It can be typically abused (hey, I'm supposed to have 20% for "other projects", but I have a deadline, so I'll use it for the "regular work"), but at least there is a line in the sand saying: "This is clearly time for OTHER STUFF". Your manager can say to you "hey, it's friday so you should be leaving this alone and do alternative projects" 100% sounds great, but does not define anything, so it's extremely easy to fall into "I have a lot of work, I can move to other stuff when the workload goes down". Of course, workload never goes down...