Of course not. What argument could I give you here? The only thing I can give you is that on previous firmwares, the minimum frequency was 125Mhz, and then it was upped to 250Mhz. You can guess that was done because:
a) It was unstable at 125Mhz
b) Power savings were negligible
c) Nokia is evil*
d) Nokia is incompetent**
e) All of the above
Choose your own option.

So a kernel hacker telling you that is a "thin argument"?

You might say "so I know that the 3530 has its lifetime reduced by a half when working at OPP5, thus I'll consider that a similar clause applies to the 3430 and thus I'll do it". Fine. But at this point, the 3430 datasheet might say that either OPP5 is completely fine and does not reduce lifetime, or might say that OPP5 reduces lifetime to 1/18: we don't know.

Of course, does it matter to you? That's the issue here. You don't care, you want higher clock speed, you will replace the device in 6months either way (which btw is the average shelf time for $600 phones), ...

*If you think "Nokia is evil", consider that they did increase the maximum operating frequency of the N800 in a firmware upgrade when they found it safe to do. God, is it so hard to understand that Nokia is composed of people that also want to reach the device limits?

**If you think this is the case, we might even get Nokia to make it happen in the official kernels. Feel free to file a enhancement request!