[tor-relays] relay uptime and stable flag

Dear All I see some relays with uptimes over 100 days (eg. Pandora14), but they don't have the stable flag enabled ... In the FAQ page it says that relays are marked stable when they are running for more than a day, however in the directory service page I see relays which are running for more than 200 days but not marked stable and some which are running for about 3 hours already have the stable flag. Why is there this difference ?

Thanks Sambuddho