Some kids are just more susceptible to ear infections with or without tubes. My boys have them with allergy attacks, colds, teething and other things. The one thing you want to try to avoid is alway running to the doctor for oral antibiotics. Because one type of anitbiotic will leave the kids more susceptible for other germs which needs something different. See if you can use the ear drops instead.
Now there are also things that you can do, like no swimming until the tubes are out. Cut back on exposure to other people, carry hand sanitizer with you always and use it often. Especially when in pulblic areas. Be sure to wash handles on doors and faucets every day.
Milk and dairy can increase secretions in the sinuses which can back flow into the ears through the Eustacheon(sp) tubes. Your boys may be intolerant to something you are feeding them which can cause the same symptoms. Wheat and nut products, preservatives in ready made foods, baked goods and pasta mixes were all things we were told to cut out of his diet as much as possible. We did our best to give up non vegetable carbs durning outbreaks.
My older boy didn't have tubes but we finally beat the infections buy moving and taking him out of the daycare he had been in. We had a few more once he started school but by then we knew how to change his diet to get him over it really fast.