How long for lust to turn into love?

My last relationship was SERIOUSLY intense: great sex, emotional discussions, talk of soulmates etc. But after 6 months we started uni; it all fell apart within weeks, with her cheating on me.

Now, we both seemed to be thoroughly invested at the time and spent so much time together which leads me to think that it was just lust, strong emotion and need mistaken for love. So is 6 months, prior to trying an LDR just not long enough for some or can I assume that we just weren't all that suited to each other? Like I said, there was great chemistry and strong emotion, in addition to shared interests, I'm not sure what was missing tbh?