Your Account
Official telegram.org Source
Telegram is not a commercial organization, and we value our disk space greatly. If you stop using Telegram and don't come online for at least 18 months, your account will be deleted along with all messages, media, contacts and every other piece of data you store in the Telegram cloud. You can change the exact period after which your inactive account will self-destruct in Settings.
Official Telegram Reference: https://telegram.org/faq
Part of the TGWAY.com Official Telegram Knowledge Base (98 Verified Q&As).