The user can return to the invitation link at any point to access the tenant/resources. It won't change anything about the user's redemption status though. If the user has already redeemed the invitation, the user won't be able to re-redeem it.
In the past when an invitation was already redeemed and you wanted to update the user's sign-in information, you had to delete the user and re-invite them. But now you can reset the user's redemption status if needed. https://github.com/MicrosoftDocs/azure-docs/blob/master/articles/active-directory/external-identities/reset-redemption-status.md
Let me know if this answers your question.