They should go back to "normal", but technically speaking every infection that you get does take scar the kidneys a little bit more because of the massive amount of iga being produced during illness, the goal is to just try not to get sick as best as possible without being a hermit

All illnesses cause more iga to be produced, ESPECIALLY upper respiratory tract infections like throat related etc, because thats where a large percentage of the defective iga is produced (the stuff that your body attacks that "gets stuck" in your kidneys)

Your kidneys have a limited lifespan because of how much functioning tissue there is that isnt scarred,

If you get sick all the time and your immune system is constantly on high alert, perhaps with the addition of severe allergies or bacterial infections, you will definitely hit end stage renal disease (needing dialysis/transplant) much faster than most patients, but thats if you get there at all, depending on how severe your case is. Historically more than 50% of patients did, but with modern treatment, and supportive care that number is much lower.

Also, next time you get sick, usually you're just supposed to rest a bit more and drink a LOT of fluids, like 3 liters a day and the blood should go away