What are the additional phrases named? In terms of the alerts for example, I can see these:
exup_alert_purchased_user_upgrade
exup_alert_expiring_user_upgrade
exup_alert_expired_user_upgrade
exup_alert_expiring_user_subscription
exup_alert_upgrade_payment_reversal
The only one which seems applicable for the approaching expiry warning of a standard user upgrade is exup_alert_expiring_user_upgrade.
Are you saying there are already two in this case, one for users who will be presented with an Extend Upgrade button and another phrase for those that won't be able to renew until their current upgrade expires?