Sure, If you make it your own policy to work on one client at a time, you could have downtime that you still charge for. It doesn’t have to be this way though,

Sure, If you make it your own policy to work on one client at a time, you could have downtime that you still charge for. It doesn’t have to be this way though, retainer does not mean you have to be limited to one client. If you feel guilty that you don’t provide enough value for the work you do, go ahead and charge a half daily or a daily rate, and work on other projects on other days. Personally I will take on 1-2 clients max because that is all I can handle at a time without outsourcing parts of my process (have yet to try this). Essentially you can end up with 2 higher paying “jobs” and charge twice or 3 times what your colleagues are making in-house. It all depends on how you want to do things - you’re the boss.