Now, seriously – in my experience, it happens very rarely that friendship becomes more. It’s quite unlikely both fall head over heels in love after knowing each others for years, and friendship always becomes hard to maintain if “love side effects” like jealosy or different needs of being close to the other come in.
However, if it happens (which usually isn’t “falling in love” but a growing sense of belonging together), I think it’s more likely to work in long term, as you’re not “blinded by love” and everything crashes when you start to see the other as (s)he really is (instead of a hormone modified human seen by a hormone drugged brain).