being a flashaholic and having owned hundreds and hundreds of 1xAAA lights, i can tell you that there is no such thing as a totally-reliable light. everything ever made by humans is capable of failing. that is why one should carry back-ups. but some designs are more inherently reliable than others. so with that said:

of all the cheapies the Fenix E01 is the most-reliable best-buy for long-runtime survival needs. (under 10 lumens)

for a general use EDC light i much prefer the beam shape, tint and brightness (27 lumens) of the Fenix E05, but runtime is much less.

for ultimate reliability and extreme-long-runtime in a 1xAAA survival light, there is nothing quite like the custom Mako. they were made in small runs and cost around $150. if you're committed and well-heeled, now and then one shows up for sale on CPF's BST Ti forum.
here's a thread i posted about them: Mako-1xAAA-the-most-important-flashlight-i-ve-ever-owned

re: Thrunite Ti - i've owned a few of them. nice light for the money but the tiny metal tab that controls the hi-low stages is far too small and fragile, which eventually leads to problems.

my EDC rule is "the smaller the better" so that you'll always have it with you. for that i like EDCing the DQG Tiny, currently the smallest 1xAAA in the world, which is made in stainless, has two stages (around 5 lumens on Low and 60 lumens on High), two different tint options (the warmer versions can be found here), is reasonably priced, and pretty reliable (for the half dozen Tinys i've had the pleasure of owning).