> I don't want to retire. Why would I? I generally feel the same way, but even in my mid-30s I've noticed that my energy levels have definitely trended downwar

> I don't want to retire. Why would I? I generally feel the same way, but even in my mid-30s I've noticed that my energy levels have definitely trended downwards over time. And I'm doing all the right things: eating healthy, exercising, using standing desk, etc. Nothing too extreme at this point, but I also notice this trend in older relatives and coworkers, so the possibility of this happening to me seems very real and worth planning for. If it does, there will be a point where I don't have enough energy to put into a full-time job plus everything else I need to do to live, and so it'll make sense to retire then. And if I end up feeling just as spry as I do now in 40 years, then sure why not just keep working?