Yes - per the Official Rules YottaCash and Tokens can expire after 30 days of account inactivity. You must login to your Yotta account at least once after 30 days to maintain your YottaCash and Tokens.

Official Rules section 4.9.1-2

YottaCash are only valid for 30 days from the date an Eligible Participant last logged into their Customer Account and when they automatically expire.

Inactive Accounts. If an Eligible Participant does not login to their Customer Account within a 30-day period or their account is otherwise deemed inactive in the sole discretion of Yotta, Participant will forfeit any balance of YottaCash and unclaimed prize winnings. Unless Yotta agrees and decides otherwise, YottaCash are only valid for thirty (30) days from the date the Participant last logged on to their Customer Account and will thereafter automatically expire.

YottaCash may also be forfeited if a Participant’s Customer Account is closed or terminated for any reason, including at the Sponsor/Promoter’s discretion.