This is an interesting question - and the responses, and different philosophies behind them, interesting as well.
In our case, we have a few different timelines we're working to, with different layers of 'idealness' to the life we'd have, depending on which one we reach. At the moment, I'm our primary income by a long stretch. I'm also eleven years older than my partner, and there are some things going on health-wise, with me (genetic disorder - very mild manifestation of it so far, but not sure how long that luck will hold) that may mean I become unable to keep up the kind of pace required for the income I'm currently bringing in.
We have a short-term goal, which is an amount sufficient for the family to be okay if I have to stop working precipitously. On somewhat pessimistic assumptions, if I can keep going for another five years at my current pace, we'll hit that goal - I'll be able to 'retire' then, and we'll be 'okay' with careful ongoing attention to our expenses. If we're in that scenario, an unexpected windfall would definitely make a difference to how we live, because that's an emergency planning scenario, not an ideal early retirement dream.
If my health is going okay, and I can stick it out at work for ten years (again, this is making very pessimistic financial assumptions, so the timeline is very conservative), this would enable me to retire meaningfully early, and would enable my partner to retire at the age they currently want to (which would be later than me - but would balance out, since I've funded us through periods of their study, etc.). This would give us a very comfortable life with which we'd be very happy, and which we're looking forward to. It wouldn't, however, enable us to do lots of stuff for other people - it's a life based on meeting our own fairly basic needs, plus the extravagance of needing to go, possibly for extensive periods of time, to help aging relatives overseas.
Even in the second scenario, however, a windfall would make a big difference - not so much to personal lifestyle, but to the capacity to do things for others that we would genuinely enjoy. I'd love to be able to put together a research institute in the area I work in, and to fund other kinds of research that I couldn't personally be involved in, but think are hugely important and underfunded. But my health isn't such that I think I can manage the extra work that would be required to get the money together for this sort of thing myself... But, just to make clear: it would add meaningful and significance pleasure /to my own life/, if I could be involved in something like this - I'm not saying 'look, there are charities I could donate to and be altruistic'. I'm saying: if I could engineer my absolute ideal life, I'd end my days involved in administering these kinds of funds - I'd get immense enjoyment from this.
The actual retirement goals we're directly /aiming/ for, are too modest to allow for this kind of ideal. But I expect we'll still be more than happy to hit those goals.
Weirdly, we probably will end up with some sort of unexpected windfall - or, at least, my partner will. There's some sort of trust set up by a long-deceased grandparent that, once it's funded the educations of all the grandkids (my partner was the eldest of those), will split the remaining funds amongst the beneficiaries, and probably other things we don't know about. We don't plan based on that, just like we don't plan for my partner, who's currently just started studying for a PhD, to land a lucrative academic position right on graduating - as I said above, we run on pessimistic assumptions when planning our timelines. But some of these things we don't plan for will happen nevertheless, and they probably will make a difference of some sort. But not the kind of difference worth working longer, in failing health, to achieve...