Thank you for the excellent article on upgrades.
After 12 cruises I suggest that you select your cabin and do not worry about upgrades. I had the unfortunate experience of going TBA - 14 day cruise to Europe (least expensive cabin) and found out that when my cabin was assigned, that my cabin was one of the worst on the ship. Fortunately we were able to find another cruise that had a cabin in a much better location (outside as compared to inside)and the itinerary was also much more interesting.
I would go TBA if the price is right but these days that is very rare.