Converting your indicator lights to "running lights at half power" simply means they will be receiving not 12 (13.8) V but a mere 7-8-9 V, and glow dim.
That's all.
A light bulb is actually a thermal machine, i.e. you have current flow through the filament, it heats up to the point it glows and emits light.
But the filament will be HOT long before it will emit any visible light, so don't worry on the issue of "overheating" the light bulb.
On the other hand, I have seen melted indicator lenses, but only because that indicator light had been stuck "on" (i.e. not flashing) for hours on end;
the light bulb was good at its job and survived, the lens was not meant to be exposed to all that heat and melted.
RIP... new lens, please !