Advice Please

Do you guys think the phrase “once a cheater always a cheater” is true? I’ve been talking to/dating this guy for 7-8 months and I went out with him last night. I was talking to him about past relationships and he told me that in high school- which was about seven years ago for him- he wasn’t very faithful. He said he’d date multiple girls at a time. He said that was back in high school and he isn’t like that anymore. He’s never given me any reason to not trust him. He’s very honest to me and I do feel like seven years is a long time to change. I feel like since he confessed this to me, I shouldn’t be too worried, but what are your thoughts?