I reformatted my whole OSR2 to help with mitigating heat.
Threw the Servos on these mounts and screwed them into a VESA plate
https://www.amazon.com/dp/B07Q2VP8P4?psc=1&ref=ppx_yo2ov_dt_b_product_details
Then attached some heat Syncs to them.
https://www.amazon.com/dp/B07ZNX839V?psc=1&ref=ppx_yo2ov_dt_b_product_details
Heat Syncs can also be added through the typical OSR2 setup and a fan can be installed such as:
https://www.amazon.com/dp/B00NEMGCIA?psc=1&ref=ppx_yo2ov_dt_b_product_details
This isn’t my rig, but you can see you can cut out part of the cover to throw in heat syncs:
You could also buy higher grade servos made of Titanium such as the HiTechs
https://www.amazon.com/dp/B06XF2JC5D?psc=1&ref=ppx_yo2ov_dt_b_product_details
Or you could opt for a brushless servo which wears far slower. Can’t recommend any because I have not gone that route yet