If you take 600mg of test a week, it WILL aromatize into estradiol. No maybes about it. Some guys notice the effects of estradiol more than others though. For comparison, most guys don't feel it when their blood pressure is high. But just because you don't feel anything doesn't mean you can leave it high. The only way to truly know where your estradiol is at is by getting blood work done. Where did your come in while running 600mg/week of test?
Are you familiar with the aromitization process and how AI's are used? Are you familiar with the role E2 plays in the HPTA?
You do not want to keep an AI "on hand". You want to use it when you begin your cycle to inhibit aromatization. High estradiol is bad for you in many ways. It did more to you than just that bloat it gave you last time.
If you are going to use AAS, you have to be prepared to use an AI, HCG and SERM's as well. Otherwise you are not cycling responsibly.
Oh... and let's do a better analogy to your Antibiotic usage. Do you prefer to get a vaccine for Polio or do you want to have some meds on hand to treat it after you contract it? Not every body says keep it "on hand".