Do you have to have a very structured day in order to ensure the companies you work with are successful or find you can work spontaneously at each?
I'm mostly "forced" to work spontaneously at each, depending on current needs, but whenever I can I try to structure my day around the most important tasks for each company.
Apart from Diffbot and SitePoint I also freelance for other clients, so I make it my goal to handle all the tasks for a specific client in a single day (most clients have a limited hour budget for me per week, and this usually fits into a heavily filled workday).
The exception here is SitePoint for whom I work full time (so the other clients get crowded into timeslots after that), so 16 hour work days and 7-day work weeks are not uncommon.
One might be concerned about burnout due to the high workload, but I've been doing this for a while now and don't feel fatigued yet (probably because I genuinely enjoy it all), and I'm trying to think as long-term as possible in regards to finances. The situation in Croatia isn't exactly stable, and I'm trying to set up my family for the future as best I can.