Is "once a cheater, always a cheater" a fair assessment?

Today I'm responding to a letter from Kian, a 27 year old gent from St. Louis. Let's have a look: 
Hi Michele, I'm writing in because I'm getting conflicting answers from the people I actually know and I've noticed that you and your readers tend to just speak plain. I'm dating an incredible woman, she's a little older, 32. We've been seeing each other for almost two years now. I knew she had been engaged before and it really didn't bother me. 
I just found out (not from her) that she's been engaged twice and both times the relationships failed because she was unfaithful. I'm not lacking in self-esteem and I have a healthy amount of ego. I mean to say I'm not worried about not being enough man for her or whatever that syndrome is. But as I start to consider asking her to be my wife, I'm valid in having a concern, right? 
Every situation is different but at the very least, I should discuss with her before fully committing? How much of a person's history can you really judge them for? A person with a history of infidelity doesn't necessary repeat the pattern or do they?
Kian, that is discussion worthy at the very least. As a matter of fact, I'm a little confused that you asked others (and me) about this before speaking to her. It lets me know that you probably already had some reservations? Not a condemnation, just an observation. Yes, the fact that she cheated on her two prior fiances is troublesome and you would need to understand 1) if it's true 2) why she did it and 3) what has changed/matured about her that she wouldn't do it to you. As for how much of a person's history you can judge them on - well, none really. You can take their past into consideration but you really aren't supposed to judge them for it. Glass houses, rocks. Judge not... all of that. Realistically however, I understand giving a healthy side-eye to someone with a sketchy track record. You two have been together for two years though, any worries prior to hearing about her past two imploded relationships? Just something to think about.

BougieLand, what say you? Once a cheater, always a cheater? If they cheat with you, will they cheat on you? Would you date someone with a history of infidelity? Thoughts for Kian? Do share...