Don't understand your question. Most people have their birth certificates issued soon after they were born.
So those are all "old"???
I don't think any adult has "new birth certificate"
Well ... not exactly. Personally I'd say if you can get a new 'extract' / copy of your birth certificate, and if you think a bit less likely to get some officer finding the form old dodgy or thinking it's not a valid birth certificate (because old and with a weird name), then sure, submit a new one.
So background:
-most places with a civil registry will let you order a 'new' birth certificate. (Note, no way this info can be universal, but many many countries provinces states etc have similar procedures, or at least similar in the main).
-They might call it different things, long form/short form, record of live birth (older name that), blah blah blah, doesn't matter. But it's NOT really a printed version of the original data - it's a new print-out of the data from the original acc to the new form. (Might be called an extract or a duplicate or whatever - doesn't matter - but should almost everywhere be on fancy paper or with an official stamp.) Okay, some places might actually send you a photocopy or printed copy of the microfiche records.
(My birth certificate original was a very different format than the new one I ordered a year ago, with different name and everything)
And why might this be better? Civil registries in lots of places consolidated (e g from parishes or some other sub-set) and changed the names of the forms and the like. Name of issuing authority might have changed. And in some places there's confusion about the piece of paper that might be issued at the hospital, which could be called almost anything but just a doc you have to take to the govt to get registered (or it gets done automatically), and the one that's later issued by the civil registry that is the actual birth certificate. And some old ones just don't photocopy well. (Although some new ones don't either because made to prevent copying)
Anyway: I'm not discouraging anyone from using their old one. But if you want to keep the old one, do not send the original, it will nOT be returned by IRCC. (IRCC mostly accepts photocopies of those in English so shouldn't be sending originals anway...)
Or, if you're getting documents anyway and think it might be a good idea to have an extra or current one, and it doesn't take you much time to order a new one, then why not? It probably won't cost that much or take too long (and if you're from a place where it does take a long time, you might want to order just in case and stick in a safe deposit box)