As long as you can keep using it, whatever is fine.
この場合、次のような言い方ができますよ。
A: Do you think countries need to change their coins and paper currency sometimes?
「国々は時々硬貨や紙幣を変える必要があると思う？」
B: As long as you can keep using it, whatever is fine. You don't need to go to the trouble of changing it.
「使えるならなんでもいい。わざわざ変える必要はない」
As long as you can keep using it, whatever is fine. で「（お金は）使えれば何でもいい」と表現できます。
to go to the trouble of...ing で「わざわざ…する」
ご参考まで！
カナダ 
