No more invitations to Gmail?

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When Gmail was from exclusive use of those who took the job of getting invited from someone else to the site, it used to give it's users some invitations gradually as time passed by and they continued using their mailing service. Not a long time ago, their service change and therefore new members can sign up just clicking in the website and didn't need an invitation anymore. But can the old members keep accumulating these invitations in their accounts? Or does Gmail stopped giving these invitations because they are useless now?