@olivier51,
How, in the modern world, can one NOT be within the borders of some country or another? Are you suggesting people start thinking about the moon, or a space capsule?
So, 'beyond borders' doesn't make sense.
The gerund implies the future action of ceasing to work. So, certainly, your advice to those planning ahead would be worth their consideration. Butt what about those who have already retired? Just because they have retired doesn't mean they are stuck - they can still pick up and move to where they would be happier to live out their days.
Hence, since 'retirement' encompasses both the future action AND the completed action (FACT) of leaving the workforce, the noun is preferable to the gerund.