Board Thread:Game Discussion/@comment-210.186.58.97-20151017152328/@comment-26249703-20151017153204

It tends to be around 48 hours from free use to the next free use (timer isn't reset if you buy one in between as far as I'm aware).

There is some speculation that winning a lot of fame reduces the time for the Agent, same thing for R$ and Manager, and servicing a lot reduces time for Mechanic. RR3SeanR posted his analysis of it recently but I don't recall where and when, sorry.