Seniority is a date. The base, the seat, the schedule and the year you finally hold a line worth holding are all decided by where that date puts you on a list. So the honest unit is not years at an airline. It is years in the left seat before 65 takes the seat back.
A hiring form wants your hours, your record and your medical. It has no opinion on whether the timing is right, what you are giving up, or where your family ends up living. Work these five first. Three of them are arithmetic and the arithmetic is already done. Two of them are judgment calls, and the Squadron is where those arguments happen.
Most pilots make this decision once. The number it turns on moves every month afterward: bases open and close, the list shifts under you, contracts get signed. The account is free and it gets you the Squadron and the tools. Everything past that is for the part that keeps moving after you have the job.