Gothamloki - it costs one GC a day to keep each Leader or CEO registered. That's a payment to the GM, you don't get it back. When the registration runs out, your countries / enterprise turns orange on the portal page to indicate that registration has expired and you have a limited amount of time to re-register it, otherwise it reverts to a C3 / corporations start automatically closing.
You can buy boosters (war protection, spending upgrades etc.) that, when purchased for a leader country or enterprise, also extend your registration by one day which is the cheap way of doing it. But that's why GCs are so precious. You need to constantly renew your supply, otherwise you run out and lose your empire(s) / enterprise(s).
There are plenty of ways to keep your GCs topped up: go up levels, win ranking awards or make lots of SC cash and exchange it for GCs. You also get GCs when you extend your accoun
but if you just go for levels. keeping any country shouldn't be a problem. after level 7 or 8 you should be good to go.