The life of the ballast can't easily be predicted. The ballast is likely to run hot, especially if it is a magnetic ballast. How that extra heat is dealt with could be very important to the life of the ballast. Now, if the internal components aren't rated for the extra voltage then it may not last more than a few minutes no matter what is done with the heat.
I wouldn't do this for a regular installation. Between the effects it could have on the bulb and the ballast it is really asking for trouble.
If these are surplus ballasts going in your home garage then go for it and see what happens. If it is a paying job install the proper parts.
There are serious professionals in this forum but also a rather jovial environment. It is a bit unusual because you may have to endure some rather silly posts to get real (usually very good) answers. Overall, you may get a good laugh or two and end up reading a page or three to get the answer. It isn't a big deal as long as your main spring isn't wound too tight.