What do you think is the ideal age for you to work until?
When do you want to retire?
At what age do you want to stop working?
ーWhat do you think is the ideal age for you to work until?
「あなたにとって働ける理想の年齢はいくつだと思いますか？」＝「何歳まで働くのが理想ですか？」
ideal age で「理想の年齢」
ーWhen do you want to retire?
「いつ定年退職したいですか？」
to retire で「定年退職する」
ーAt what age do you want to stop working?
「何歳で働くのをやめたいですか？」
to stop working で「働くのをやめる」
ご参考まで！
"What's your ideal retirement age?"
"Until what age would you ideally like to work?"
"How long would you like to keep working?"
"At what age would you like to retire?"
「何歳まで働く」は英語ではよく
work until + 年齢
keep working
と言います。
「理想ですか？」は
ideally
ideal
を入れると自然です。
カナダ 
アメリカ合衆国 
