Seriously
I worked at a place for 15 years and in the back of my mind I knew I was probably underpaid. But I like my coworkers and didn't want to leave them. I was a nurse in long term care, I supervise RNs. Been doing that for around 10 years. I fought tooth and nail for my nurses, I let them organize strikes and such in my office under the nose of corporate for years.
So a while ago I was stressing about my commute and started looking around for jobs near my house and found out my current salary was the rate for the new grad RNs. My 10 years experience and the fact that it was a position below me? Worthless apparently. Put out some applications and had 3 interviews within a day. Put my notice and left. Got a big raise with less responsibility. Now I visit my old job about once a month and spread dissent and encourage them to fight the good fight.
So I know it gets comfortable after a while and it's hard to imagine leaving a job after a number if years. But it's worth it. I used to think I'd retire after that job, I felt trapped there. But they don't care about you. You are a rock they will squeeze until you are out of blood.
So do it. Quit. Just because you've fallen into the 'lifer' cohort doesn't mean you don't have options.