We can buy cheap Bento at our workplace, so I buy them all the time.
この場合、次のような言い方ができますよ。
ーWe can buy cheap Bento at our workplace, so I buy them all the time.
「職場で安い弁当が買えるので、よく買います」
I buy them all the time の代わりに、I buy them almost every day.「ほとんど毎日買います」とも言えます。
ご参考まで!