Do you think heat plays any significant role? I am typically a light braker, but say on a large hill where engine braking is not enough I try to do small bursts of braking rather than sustain a lesser pressure the entire way so the heat can dissipate. I was told to do this when I was learning...
If it was me, if I had enough work I would walk away
If I needed the work, I wouldn't want my pay tied up in a bond for however long as I am struggling a bit anyway and I would do exactly what you are doing, some pay now, some pay at the completion of the project based on quantifiable tests...
I always think about this sort of things in terms of acceleration/deceleration. The human body can only tolerate however much acceleration before whatever happens internally, externally (or when internal things become internal). The whole point of the crumple zone (at least as I think of it) is...