You are eligible for unlimited "space available" upgrades.

The devil, of course, is in the details, and CO's definition of "space available" might not coincide with yours.

While you might imagine that "space available" means available seats in FC at your upgrade window, the fact is the definition of space available that CO uses is the inventory that revenue management has not set aside for revenue seats.

As you get closer to your flight time, RM shifts any remaining inventory to upgrades, often waiting till the last possible minute.

Regarding the sell-ups that are available for non elites, these are supposed to come out of the same inventory asset aside for elite upgrades.