Jay:
I'll answer, but don't listen to me -- wait for some of the smarter folks to weigh in on your question

If the pages are old and browning, I'd say do what is necessary to save the stamps. It's unlikely those old pages are acid-free, meaning they will continue to discolor and if it hasn't already, the discoloration will spread to the stamps.
If the stamps are mint, soaking them will obviously remove the gum and affect the value. But personally, I would prefer "mint no gum" to "no stamp". If they're stuck only (s)lightly, you might try just a little steam to loosen them. Allow them to dry thoroughly, then remount on newer pages. I think you said in another thread you were comfortable with soaking, if it comes to that.
Finally, you'll have to decide on hinges v. mounts. If they've already been hinged, there's no real reason not to re-hinge. But for older, hard-to-find issues, I feel more comfortable with a mount.
Well, that's my $0.02 worth. I'm sure some other folks will have even better suggestions.
KirkS