How old is too old (LJ-wise)?

Sometimes I don't read LJ for several days and can find myself going back nearly 200 messages on my friends page. That can be 3-4 days and I sometimes hesitate to comment on entries that old, feeling that it's no longer relevant or the person/conversation has moved on.
What do you, my friends, do and what would you have me do if I find an old entry of yours?
no subject
if that doesn't seem quite apropos, send email with a link to the post.
your comments are often on-target, and so very useful.