I only need to hear something once, and I don't usually forget it after that.
ーIf I hear something once, I usually remember it.
「一度聞いたら、大抵覚えている」
to hear something once で「何かを一度聞く」
to remember で「覚えている・記憶している」
ーI only need to hear something once, and I don't usually forget it after that.
「一度聞くだけで、大抵は忘れない」
only need to hear something once で「何かを一度聞くだけでよい」
to forget で「忘れる」
ご参考まで!