tickets can't be upgraded or added to past 14 days from the first use of the ticket. The no-expiration feature means all of the entitlements never expire, but your ability to add/upgrade still expires as noted above.
Tickets can never have more than 10 total days on them at any point in their lifespan. In other words, there are NO circumstances where you can buy a 10-day ticket, use some of the days and then "reload" that same ticket.