I agree w/Dodgeman and Henry (NOT that I'm 'against' Bill - it's just that I'd move slowly and check around.)
The principle is that you put this paint on the UNDERSIDE of the roof or on the INSIDE walls of the house. This implies that the heat is, first, absorbed, by the roof and/or walls, THEN reflected out. To me, this would accellerate the aging of the sheathing. Now, if this paint was touted for the OUTSIDE of the roof or OUTSIDE walls of the house, then I'd be quite a bit LESS leary. Why? Well, for starters, WHITE paint doesn't absorbe heat as much as, say, tan paint or light blue paint or any of the darker paints. Hence, you get a radiant barrier on the OUTSIDE of the house. In this scenario, the sheathing/walls don't absorbe heat.
Now, to get more confusing, if there was a paint that you could use on the INSIDE, HEATED portions of the house to keep heat IN the house, well, that I could see. It would simply be used IN CONJUNCTION with good insulation in the walls.
I wish I could say 'go for it' but I'm a bit leary. My best to ya and hope this helps.