I have been running my ESPRESSOBin in production since the day after I got it, with no heatsink and without issue. That said, I haven’t run any super intense workloads on it, as it is being used for NAS mostly, not computation and I compiled my kernel on a different system.
Also, just to be fair here, I do have it mounted in a case where there is plenty of airflow so this may also be why I haven’t seen the overheating issue.
TL:DR:
I haven’t seen any overheating issues yet with my boards and I am not using any heat sink or fan. Haven’t tested under extreme workloads, but at the same time I do have it in a place where it is receiving passive cooling by fan.
Good luck to you guys figuring out something that works for you!
Cheers!