Depends if there's a legitimate reason - 2 roles ago I was there for 3 1/2 years and my manager basically said to me I'd do best in my career to leave by then (

Depends if there's a legitimate reason - 2 roles ago I was there for 3 1/2 years and my manager basically said to me I'd do best in my career to leave by then (loved working for her), previous job was 18 months and was doing well, but my current position came up and was something completely different that would be a fantastic development experience. However, I don't think it's a good fit, both from mine and the company's perspective - do I stick it out to ensure my resume doesn't have a half life, or would a next employer understand it was something I had to jump to, but was in everyone's best interests not to drag it out? (we're talking <5 months)