Actually, depending on how bright you want a light to be, maybe you don't really need to switch. I believe the runtime between your coin cell Photon and a 1xAAA Fenix E01 is going to be roughly similar. The E01 should be brighter, but in true darkness, you don't need much to get by as long as the light is focused enough so you can point it at what you want to see (and why the unfocused light from mobile phone screens are a poor substitute for a flashlight).

The Photon might be less convenient because you have to continually squeeze it (hence the reason why I carry a Photon II with a switch), but conversely, using the Photon intermittently will greatly increase the runtime. With the E01, you're far more likely to turn it on and leave it on continuously, but battery changes are easier and can be done in the dark.

Two coin cell Photons (say, one around your neck and one on your keys) are arguably better preparation and take up the same volume than a single "bigger" light on your belt that you're not that eager to clip on every day because you will probably be far more likely to have the Photons actually on you when you need it. The Photons just won't be able to be as bright as a bigger light can get.