As was kind of alluded to, it is not the watts so much as it is the amps. Any decent mechanical switch can handle up to 50 volts or so without any problem whatsoever. On the other hand, high current is another matter. When working with higher currents, resistance can show up in the most unlikely spots, like the springs mentioned above, and high current can pit/soften/melt switch contacts without much problem. From what I have seen from looking at specs and reviews, it appears that the average switch tops out at about 4 amps, so with 5 26650 cells in series producing around 18v, somewhere around 80 watts looks like an upper limit without some mods as far as springs and switches go.