From a forum in the US:
I don't know about you guys but for my kind of flying I only update the database once a year. I routinely fly to 5 airports only to visit relatives and nothing has changed at these airports except fuel prices. Like in the old days of Delco INS it is perfectly legal to fly with an expired database as long as the pilot has verified the waypoints either by published data or by actual flight. A new unverified database can have errors. There is also a risk of screwing up your GPS everytime you update. Save the money on updates, and use it for AVGAS to keep you flying.
Anyone ever heard of such a (let's face it - practical) rule applying in our not-regulated-quite-enough-yet country?