Like Suz, I can't leave this thread alone now that I've found it.
To get back to first-wave feminism for a minute, Gloria Steinem famously said "This is what 40 looks like," and Carol Hanisch famously said "the personal is political."
So on the one hand, one could argue that it's fine to embrace the term "old lady" for oneself if one finds it empowering. That's part of a long tradition of oppressed groups embracing pejorative terms and finding that empowering. See, most famously and controversially, African American rappers and others embracing the reviled "n-word."
But... I think any time we append a modifier to the term "woman," and any time we use the word "lady" at all, but especially with a modifier like "young" or "old," we bring up stereotypes that I personally don't want applied to me. The term "old lady" conjures up someone who is weak at best and cranky and unpleasant and frumpy at worst. None of those things apply to me, I don't want anyone to think of those things as applying to me, and rather than fight the associations I'd just as soon not use the term. The term "old woman" isn't quite as bad because at least there's room there for wisdom, as Deb points out above. But still, you don't generally hear men described as "old" until they are very very old indeed, and I'd just as soon reserve the term "old" for myself until I am very very old indeed, as well.
And I kind of think, with all love and respect to my sisters who feel differently, that embracing the term "old lady" in one's 50s and 60s and even 70s is perhaps both inaccurate and promoting outdated stereotypes and ought to be done with extreme caution.
The end.
