I think it would need to be at least $500,000, and perhaps even more than that. I recognize that as an obnoxiously large number. But I'm not working and DH will likely work at least another 4 years for reasons outside money. By the time he gets to that point, we will be FIRE. An extra $100k, for example, means $4000 a year. I don't see that really affecting our lifestyle in a way that would feel significantly different. Probably an extra or longer vacation each year and increased charitable donations. At half a million and an additional $20,000 a year, things would change in a way that wasn't just a few more fun, but appreciated, things. Like taking a group of people we love on vacation every year, finding part of college for friends' kids, considering building a dream home from scratch, etc.