This is a fascinating thread, and I agree with 99 per cent of what's been said. One thing though - never forget the vicissitudes of fate which, although are sometimes kind, can sometimes be very cruel.
Dh worked for a large global company at high management level. We had lovely house (with small mortgage) in affluent part of Berkshire. With 4 dc to provide for, we didn't live a particularly lavish life, but were comfortable enough for me to be SAHM. About 10 years ago DH's kidneys, for no apparent reason, gave up the ghost. About 5 years ago his health got too bad for him to continue working. He was forced to give up.
We get by ok, partly due to having been sensible when we had a high income, partly due to downsizing and changing the way we lived. I work now too (though not for very much). It has been hard. I think the point im trying to make is that sometimes, no matter how hard you work, how many hours you put in, how careful you are, how passionate - you can still be blindsided.
My PIL are very wealthy. They are also very mean careful with their money. Not once have they offered to help out their son (my DH) during his illness by contributing in any way. They did however once send my 4 dc one gold chocolate coin (admittedly a large one) for easter. I am guessing it is by this sort of careful money management they have become wealthy (bitter, moi?).