Are CO₂ tire cartridges reusable for multiple tires?
CO2 cartridges are fine if you use them in the intended way: Roadside emergency. Otherwise they are a terrible waste of energy, resources and money. Normally a single cartridge is just enough for one tyre. You will also lack means to control the pressure that you put into the tyre. Which is OK in an emergency where you just need to have it inflated and eventually be able to move on and get home

In this case, you better invest into a decent track pump with a pressure gauge that you will get for a dozen or so cartridges plus applicator.

Note: a cartridge is for one-time use only. If you inflate the tyre and store the cartridge in your saddlebag because there is still some CO2 left, which is difficult to estimate anyway, the cartridge will empty completely within the next few hours. The system isn't that well sealed against leaks of the remaining gas.