I inherited this server from the chap who set it up but I now can't contact him. Have taken a look through config, faq and done searches but can't seem to see anything. Can someone point me in right direction if I have missed where I can change the default setting of how long a shared link takes to expire. I believe it is set to 12 weeks and I have been asked to increase this to 24. I know you can manually set your own expiration date but apparently that is too hard 
I don't know how it is in 8.2, and it is not supported anymore, but in 9.0.9 it can be configured in the web UI in the sharing section: