pert:
Also posted to the issue tracker:
Arduino 1.7.10 NO Borad manager · Issue #6917 · arduino/Arduino · GitHubI've already responded regarding the 1.7.10 issue on your issue report but I think this is a good place for us to do preliminary investigation of the mysterious "lot of error" you mention. If we determine they are caused by a bug in the Arduino IDE then you can proceed to report them on the Arduino IDE issue tracker but maybe we can resolve them here without having to involve the Arduino developers.
Please install Arduino IDE 1.8.5 from http://www.arduino.cc/en/Main/Software and then post the full text of all error messages you encounter as well as any additional information that might be helpful.
Wow, pert, I went to sleep for a few months after installing V1.6.9 and already we're up to V 1.8.5.
Mate, I've got to ask, is there any real benefit in upgrading at this point, or should I sit on my hands for a bit longer?
V1.6.9 still works fine for me, and is very stable. I'm worried that upgrading will result in some earlier stuff not working when I provide firmware upgrades to customers. (Not that I have many customers - I've well and truly reached retirement age, but I must look after my people as long as possible. 
)