As I see it:
1. You pay 12 months membership or full license upfront, you own the license forever.
2. If after 12 months you renew membership or (if you payed upfont) start paying monthly, you get upgrades, and they are yours, forever.
3. If after, say, 19 months membership, you cancel it, you own everything you received, forever.
4. If after cancelling you acquire membership again, say, 5 months later, you receive those 5 months worth of updates, BUT you do not own them, so:
5. If you cancel membership again before you pay 12 months or the price of a full license UPGRADE ($199 or so), you roll back to the point when your initial 19 month membership ended, but:
6. If you do pay for those 12 months, everything you receive until the next time you let your membership expire is yours, forever.