I usually have 3 to 7 days to know whether I will be able to overcome an exacerbation without antibiotics. It depends on how quick and how severe the onset is. Like sometimes, I feel that I'm getting slowly sicker over several days and then it peaks after 5 to 7 days. When the onset is this gradual, I know that I can overcome it in 1 to 2 weeks without additional antibiotics. I take it like it's just normal ups and downs of the body. However, if the onset is faster and more acute, then it's probably because something caused my immune system to be weaker, like a cold virus and I know that I'll have trouble overcoming it without antibiotics. Well... I could still overcome it without antibiotics, but it would take long and would likely cause unnecessary damage to my lungs.
I do try to avoid taking antibiotics when I can. My pseudo is already resistant to many penicillins and I can't take Levaquin, so I don't take any Cipro unless I REALLY need it, to avoid problems in the future. Cipro has already started working less than it used to.
I don't do anything specific to avoid having to take antibiotics, though I could. I could up my tobramycin dose from twice to thrice a day. I don't know if it's the right thing to do, but I choose not to do anything more than usual unless I need to. Again, to avoid problems in the future.