There is an official datasheet from TI (for omap3530 which is very similar to omap3430) with the information about the expected lifespan. Running the chip all the time at 600MHz vs. 500MHz already decreases lifespan twice, hence 600MHz is considered overdrive: Code: To avoid significant device degradation for commercial temperature OMAP3530/OMAP3525 devices (0°C ≤ Tj ≤ 90°C), the device power-on hours (POH) must be limited to one of the following: • 100K total POH when operating across all OPPs and keeping the time spent at OPP5-OPP6 to less than 23K POH. • 50K total POH when operating at OPP5 - OPP6. • 44K total POH with no restrictions to the proportion of these POH at operating points OPP1 - OPP6. If this effect is exponential, then pushing the chip above 600MHz may reduce lifespan quite dramatically. I think that TI would sell chips labeled at 1GHz if they were sure that this clock frequency is safe, it is in their best interests after all, considering the tough competition. Those who buy new smartphones each half a year may not care much, but I feel sorry for those who would buy a second hand N900, heavily worn out by some overclocker.
To avoid significant device degradation for commercial temperature OMAP3530/OMAP3525 devices (0°C ≤ Tj ≤ 90°C), the device power-on hours (POH) must be limited to one of the following: • 100K total POH when operating across all OPPs and keeping the time spent at OPP5-OPP6 to less than 23K POH. • 50K total POH when operating at OPP5 - OPP6. • 44K total POH with no restrictions to the proportion of these POH at operating points OPP1 - OPP6.