No domestic supplier will guarantee their solenoids for pulsing, they always recommend a safety solenoid in series with the working solenoid.
That's just the companies covering their butts.
I know the 3-4 years I was working with ND's, NX, Zex, etc. I never saw a failure due to "over pulsing". People would claim that and send them in for repair, and 99% of the time it was a mechanical failure due to trash in the nitrous line. Which could have been avoided running a filter.
Electrical failure's of solenoids most of the time return the solenoid to NC. If it didn't, there as bad wiring involved with the installer somewhere down the line.
I'm not saying if the planets align, pigs fly, and hell freezes over the solenoids won't fail to do pulsing. The chances though of that happening is about slim to none.
EDIT:
I may have lied to you now that I'm thinking of it. The new NX solenoids before they were really released to the public initially had problems pulsing. The problem was found and fixed. I was graduating college and getting out of that business right around that time, so my memory on that is a little fuzzy.