I was studying the use of "used to" and "would" when I came across this sentence, which has been nagging me:
1a Family values used to be quite different in those days.
1b Family values would be quite different in those days.
2a It used to be quite normal for cousins to marry.
2b It would be quite normal for cousins to marry.
3a Generally speaking, these marriages used to succeed as well as any others.
3b Generally speaking, these marriages would succeed as well as any others.
Which "b" sentences are grammatically wrong?
According to what the book* said, "used to" - not "would" - can only go along with the so-called past state. With that being said, I was easily able to make out that
1b is wrong, obviously;
3b is, of course, right, for it's telling a repetition.
But, moreover, 2b is not wrong, which is kind of weird, although I do feel it right somehow. Can somebody explain this to me?
*Grammar and Vocabulary for Cambridge Advanced and Proficiency by Richard Side and Guy Wellman"