I guess I would term my motivation "compensation instability" more than job instability. I have had the good fortune to make very good money as a consultant the past 18 months or so, and am on the verge of taking a new contract that *should* go 2-3 years with even better compensation. At the rate I expect to save in the next 3 years, FIRE with basically no reduction in expenses in 6 years is pretty realistic. So, my goal is to get to a point where we could technically FIRE someplace modest before the end of this contract, and then take every day past that as an opportunity to pad the safe withdrawal rate and increase our options in retirement. 1-2 years would get us to the "safe to retire and live like kings in a low COL country" status, 3 years gets us to "safe to retire and live like kings in a low COL state of the USA" status, and 5-6 years gets us to "safe to retire anywhere we want and live like kings" status.
The trick is that I don't know what the landscape will be in 3 years, and finding another position with this kind of income may be very, very hard. I might be forced to take a position for half or less of the income, and if we drag our feet on savings and investments while income is high, that could really delay FI. I don't want to assume that the money firehose will simply run forever.