The simple answer is...
It depends...
You will find it kinda random....there is a fairly hi turnover at most bases, as people upgrade to bigger planes, or take advantage of some of the guaranteed interviews, etc and move up (yup, some folks go straight to widebodys, just depends on you, your goals) but also a certain number of lifers who are on a run/in a position that simply works for us in life, and don't plan on moving.
Unlike many places where many people commute, or have "junior" bases, most AMF line pilots (excluding HBC/floaters) live with the plane (hub or outstation depending on the route)...so a dream job for some if it happens to be where you want to live...either all day or all night at home, with the bulk of your rest in a company paid accommodations while away from home.
Some people DO move a bit to try to get more flight time, be closer to family, etc , using the bid system, but the system is effectively set up so once you are where you want to be, the route is yours, even if a more senior person wants it, as only "open" routes are bid, not the entire system.
It is a different style of life than the typical airline life, but hopefully you have figured that out by this point in your search!
Good luck with you search!