If it exists for more than 4 hours, 0 minutes are consumed - the 240 minutes are "refunded" to the pot.
Ephemeral keys can still be used to manage long-lived devices when you want them automatically cleaned up if they disappear - they'll just count as tagged nodes when they hit that 241 minute age.
Ephemeral keys can still be used to manage long-lived devices when you want them automatically cleaned up if they disappear - they'll just count as tagged nodes when they hit that 241 minute age.