I can sympathize with you so much on that.

Dusty had a weak immune system and always seemed to be sick several times a year requiring me to give her antibiotic injections at home for a week (she wouldn't take anything by mouth). All they really did was keep any secondary infections down since she had to 'run her course' with it. If we didn't get her on antibiotics she would end up with a staph infection in her throat. ewww

Jack has a basically decent immune system however has been sneezing for the last 2 years. Never has any discharge and it never progresses or goes totally away. We've tried several times with several antibiotics and it's never impacted his sneezing in any way. He's healthy otherwise (other than his unrelated mega colon problem) so we all just live with the sneezing and keep watch for any discharges or other indicators that he needs antibiotics. He doesn't seem like a cat suffering or unhappy about it, eats normally, plays, and is very affectionate.