gerund

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.

It's not always easy to pick up sticks and move to another country. Many have strict visa requirements. For example it is practically impossible to retire to the United Kingdom unless you are an EU citizen.