It's interesting to self-note the changes from the realization period, thru the prep period, followed by the actual event, then the adjustment period, and finally the I'm so in the groove mode lifestyle. And, ...how one's views of those periods adjusts over that time...
For us DW and I shared the realization that the job wasn't getting any better, and appeared potentially to get far worse, especially for her (combination of health issues and weak management) The system we both worked in once we bothered to check out the fine points of the rules and regs stated we could bail at age 50 with a modest Cola payout, basically we'd achieve about 30k per year combined. This seemed way-frugal but doable, and we determined to go for it. This was 7 years out, both of us 43ish at the moment of realization. We agreed to sock away a bunch of contingency money during the 7 year plan, my late 90's estimates indicated 100k each was possible based on the returns of the 90's so far. Oops! well that didn't pan out and other unforseen events interfered with the savings part of our plan, but OTOH the system we worked under also achieved and enhancement (I would guess based on the same 90's gains) and a late career promotion, helped balance out our final return nicely.
To answer the thread, we picked a date based on a particular age (50) and figured we'd back into the FIRE "salary" and learn to live within those future means. We didn't really know what we have to live on until a couple years before I retired. We've been doing it for two plus years now, never had to touch our contingency savings to date (planning to use it to leverage our final home in another location to the North in a year or two when the market is housing market is fully tanked, then hold onto our current home until the market recovers. Who knows whether that's what we'll really do, but it sounds good at the moment.!
We're doing alright, we're getting good grades, the future's so bright, we gotta wear shades.