GPS database - can one skip updates, and how long do they run for if not updated?

You could clone a card every month the full upgrade is available. Then update the cloned copy the second month with the navdata.
Have you tried calling Jepp support?

Timothy, I don’t have any experience with updating GTN boxes and may have only grasped part of the issue. But have you tried deleting the old ST & O data from the card on which you save a new Nav data cycle which comes without ST & O?

Timothy wrote:

Thank you. It looks like to use the Flightstream 510 I also have to get my data through Garmin and use Garmin Pilot – is that right?

Yes that’s correct. I understand that may users find Jeppesen problematic in any case.
I believe there is now an agreed method to transfer an existing subscription from Jepp to FlyGarmin – probably best to call Garmin Europe to discuss this aspect as I’m not an active user.

@Timothy,
fly.garmin allows us to “reinstall” a database:

So, instead of keeping our spare card in a flight bag with last month’s databases until next month, we should be able to update it straight away. Then when when we apply next month’s update, it will be up to date.

…but I haven’t tried it yet, so that procedure may be too easy to be true.

Does the Jepp annual subscription include more than one terrain update?

Does anyone know how long a GTN keeps running for if the database is not updated, for

• enroute
• approaches

I suspect enroute may never expire, but approaches will after something like a few months. But I have never seen any real data.