You mean when you reboot the n900?

Just run it when you actually need it - the gps eats batteries.
To run it daily or once a week maybe to tune your n900 timestamp
does not require more than a few minutes for the gps to lock in.

i suppose you could schedule a launch each day...
... not sure how you would turn it off automatically though.

Turning it on and then forgetting about it would flatten the battery.