Anything can fail. You can blow a fuse and not have any tail lights. I know it is a concern but not I think something one should worry about. Both the tail blazer and the Kuryakn one are very easy to quickly and temp put back into service.
I do not pull a trailer, scared to death to on a bike, but do have a friend who does and we called Kissan a couple weeks ago and they told us no. The amp load would be too much. So we put the Kissan on the bike normally, and then another unit in line on the trailer for the trailer. Ran a jumper wire from ahead of the tie in under the seat to the first unit to the trailer for the brake lights. So far so good. Works fine.
Another thing you can do is change all bulbs to the new generation LED, that is quite expensive, but would work. The new generation bulbs are pretty high priced. But very visible, would not want them on any lights that you need to see with, but for visiblity they can be seen better, not sure how to say this, but LED can be seen better, but do not produce light to see with?? Good on the back but not on the front, like for running lamps or fog lamps.
Kit