Hello. First of all, thank you very much for the information.
It is prescribed: "According to the Ordinance on Technical Requirements for Road Vehicles (VTS), Art. 216 and 217 as well as the Traffic Regulations Ordinance (VRV) paragraph 30 Art. 1 regulate how lights on bicycles must be equipped: "Bicycles must be equipped with at least one resting light that shines white to the front and one that shines red to the rear from the beginning of dusk until daylight, in poor visibility conditions and in tunnels" Attention: flashing lights are only allowed as additional lighting!
This means that I have to choose at least the mode "*STEADY ON - LOW" - on the homepage you mentioned, a light duration of 3 h is given, in the mode "STEADY ON - HIGH" - the light duration is given with only 1.8 h.

On my tour in "STEADY ON - LOW" mode, the light went out after 2 1/2 hours. No matter whether 1.8 h or 3 h light duration is too short in my opinion.
But that's clearly my fault, I haven't informed myself sufficiently. But I am capable of learning and in the meantime I went to my friendly bike dealer for advice. He recommended the Lezyne Femto USB Drive Pair, light duration 6 hours for CHF 39.90.

Question for GALAXUS: What's wrong with specifying the burn time of the e-bike lights?

Depends on the light level. Here you can see the light duration depending on the light level according to the specification:
https://www.knog.com/product...