Hopefully this question is appropriate here.
The .fr TLD stands for France and is managed by AFNIC. In order to register for second-level domains under this TLD, one is required to be a resident of the European Econonic Area.
I am currently a resident of the European Economic Area, but I might move away one day. Does this mean that I might lose my domain in this case? Will I not be able to prolong it any more?
Although I wouldn't be surprised if in practice the registration requirements are only checked on registration and not for renewals, you don't have to lose your domain when you leave Europe.
A number of registrars provide trustee services that allow the registration of a .FR domain to people/organisations that don't qualify directly and your domain can be transferred to such a trustee if required.