Linking the channel doesn’t leave you with permanent access: every time you send the valid code, a 30-minute session opens. While that session is active, every message of yours the system processes normally (not just the code) renews it for another 30 minutes — as long as you keep using the chat somewhat regularly, the session doesn’t expire.
Note — When the session expires
If 30 minutes pass with no activity, the session closes on its own. The next message you send is no longer treated as yours — section 7’s behavior returns (it treats you as a visitor). To reopen it, send your authenticator app’s 6-digit code again over that same channel (section 5) — the link already exists, so this second send only reopens a session, it doesn’t “link” anything again.
Important — Turning off two-factor verification closes your channel sessions
If you turn off your account’s two-factor verification (Manual 26, section 5), all your active channel sessions automatically close — 2FA is the only thing that makes them possible. The link itself (that your number/chat is associated with your account) is kept: if you turn 2FA back on, you can reopen a session with the same channel without having to link it again from scratch.