You can ... as often as you need to as long as you don't ...
この場合、次のような言い方ができますよ。
ーYou can receive medical treatment in Japan as often as you need to and only pay 40% of the bill as long as you don't exceed 50,000 yen.
「5万円を超えない限り、４割負担で何度でも日本で医療を受けることができます」
You can ... as often as you need to as long as you don't ... で「○○しない限りは何度でも△できる」と言えます。
ご参考まで！
カナダ 
