OC'ing will have no ill affects on updates, i must say though the advice you've been given is only partialy true, OC'ing can give you better battery life (but not that much) but reducing minimum frequency to 125mhz will just make your device unstable, i find i get best results overall, with ideal 500-850Mhz
before you do anything though please read this: http://wiki.maemo.org/Overclocking & http://wiki.maemo.org/Kernel_Power
Good luck, and remember over clocking voids your waranty