7610 Predictive text memory

I was wondering if anyone knew if there was a way to increase the size of
the dictionary on the 7610? One thing that really irritated me about my last
phone (7250) was its seemingly tiny memory for new words when using
predictive text input. The 7610 seems better but still forgets words after a
while. Surely the size of the memory on this phone should allow for a much
larger dictionary?

Thanks for any help.....