You do not report TI's numbers, you invent your own numbers, as you openly admit.

TI numbers are:

100K hours when operating across all OPPs and no more of 23K of those hours are at OPP5-6.

50K hours when using OPP5-6 only.

44K with absolutely no restriction on OPPs.

Where do you get those 10 years and 550MHz and 5 years at 600MHz, I can't imagine.

It is important to recall that an OPP is a predefined frequency+voltage level, so when we do not use TI's OPP (such as when we use 600MHz at a lower voltage level, or when we use higher frequency and lower voltage compared to OPP6) the effect on lifetime is unknown.

Since practically any N900 runs at more than 77% idle, we are within the parameters of the 100K hours lifetime, and the fact that a few percent of this time is spent at 900 MHz instead of 600MHz, most probably does not have a great effect on lifetime.