Bay will probably put better translated one for this one but here's copy/paste of what I got from the JP reps.
Copy/paste from my translation thread.
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On the JP grand company thread players asked questions regarding below and rep responded to them.

Original Thread Link: http://forum.square-enix.com/ffxiv/threads/16455

Quote Originally Posted by Foxclon View Post
こんにちは。
Hello

2点ほどコメントです。
Comment regarding these two
軍票がもらえるクエストで繰り返し可能なものってあるのかな？
For Grand Company quest which you can obtain company seal, are there ones you can repeat?
軍票がもらえるクエストやコンテンツは、パッチ1.19を皮切りに段階的に実装していきます。
With patch 1.19 we will start releasing quests and contents which you can obtain company seal.
正式に所属したら、他の2国のは脱退扱いになって、軍票はなくなるんだろうか
When officially assigned to one country will the other two country be considered released and will the company seal be gone (for those other country)
はい、なくなってしまいます。
ただし、将来用途が発生する可能性も踏まえ内部データとしては保持されます。
Yes it will be gone, but for future there may be possibility to use them so the internal data will be stored.