Safely testing runtime

I recently finished up a runtime test on my Armytek Tiara C1. I replaced the 700mah battery with an 1100mah Vapcel and started the test on 1-18-20 on firefly mode (.4 lumen). I am happy to report after 60 days, the light was still running strong with no noticeable dimming (anecdotal evidence, I know).

I want to run some tests on some of my other lights, but I do not want to do anything dangerous. I am not super knowledgeable on the topic, but I know that running a lithium ion battery too low can be dangerous.

My question is, what is a safe method for running a total runtime test? Is there a safe way to do so? Have any of you run tests on your lights?

I will trust the knowledge of those in the forum. I do not wish to do anything dangerous or inadvisable.

(please be gentle)