The kernel is fantastic, very fast....
The CPU and probably GPU as well are stable and safe up to 110 - 115 °C That's the real max.
But some miscalculations are to expected when it runs over 110 °C. At 120 °C it'll freeze and (dirty) reboot.
Now i'm trying to issue an clean reboot at 110 °C in order to not damage filesystem for every reboot caused by overheat since it also comes with some (minimal) data loss, unfortunately.
65 °C is too low, it'll throttle a lot when you run more than 1 thread at full load.
You can't damage the battery with high CPU/GPU temp as the battery is isolated from the heatsink.
Samsung is not that stupid.
Best for the battery is: keep charge temp to the default of 40 °C and maybe you can increase current somewhat to + 300 mA. Use the battery between 5 - 95 % and don't charge over night without to make sure that you are able to stop charging at 95 %.
Most batteries in phones die so quickly because almost all people charges over night with fast charging enabled. The problem is after 1,5 hour it's fully charged and the battery keeps 100 % for further 6 hours. In that 6 hours for every night the battery will loose the most capacity since Li-Ion batteries really don't like to be for too long at 100 % or 0 %.
That's all, if you understand this u'll enjoy your phone for many years.