I just throw mine into a book bag every day. The most useful lights, I for me, are the rear external packs, since they offer useful runtime: to do WORK. And being able to do work, you have them around in emergencies and unexpected situations. I also find these more comfortable than unbalanced front heavy lights.
My experience since 2005 is, no failures in the external wiring with store bought lights (remington, fenix, garrity). I have had several controller failures, which is the true weak link of the modern flashlight.
My own modifications is another story. Quite a high failure rate during 1 year of use on external wiring, when I convert from 3 AAA to 3 AA.
Probably, my soldering skills. Maybe someone has a thought on this.
The obvious solution is just spend the extra $30 on a Fenix HP11. But the waiting for a shipment is no fun, and also can be costly if the light can save you money on some task or offer you saftey. For fun, my last rear battery pack modification of October, I avoided this wiring risk, by using thin strips of aluminum flashing to shield electrical wires from undue movement by enclosing them (top and bottom). The wiring I did runs over top of head to rear pack, rather than the around the side.