What happens with your Membership when it expires depends on whether or not you have enabled auto-renew payments.
Auto-renew payments enabled
If your Membership is on auto-renew our system will try to do a recurring payment charge for 7 days for the applicable chosen Membership period. If the charge is successful your Membership will just continue and if the charge is not successful within those 7 days your account will be automatically downgraded to one of the Basic plans.
Auto-renew payments disabled
If you have disabled the auto-renew payment functionality your Membership will be automatically downgraded to one of the Basic plans on the next day after your paid Membership period has ended.