Advanced Carp Magazine

Advanced Carp Fishing says: Coated hooks should not rust in such a short space of time, and most carp hooks, including the ones you were using, are coated. Rusting can occur when the coating is removed, and is an issue that often arises if you sharpen the point, as this will remove the coating. As you point out, the rusting problem you experienced is likely a one off, perhaps the coating had been damaged or chipped prior to casting out. Whatever the reason, the hook pull you experienced won’t be because of this rusting. That is more likely down to the rig itself, the way in which the fish was being played, or perhaps that particular carp’s mouth was damaged prior to you hooking it and the hook didn’t find a secure hold.

When it comes to how long you can use a hook for, that entirely depends on the hook. Sometimes a single capture will ruin the point  and on other occasions you can enjoy multiple captures and the hook still be fine.
Check the hook before every cast paying particular attention to the sharpness of the point and signs of damage or rusting. If you have any doubts as to the hook’s quality then get rid of it, but if all is well then you can keep on using it indefinitely.