What are the best settings to extend battery life?

I'd like to extend the battery life of my Mini for as long as possible while making sure I'm trackable and safe. It's used mainly by my family to check I'm ok - I don't use it to send messages or look at my route/pace. I have it on 30 min Send Interval. Log interval, Auto track and Ext tracking are all Off. Any ideas of how to extend battery life?