My son is 2 years old and has been going to part-time daycare (2 TO 3 days/week) since he was an infant. The first year or so was really tough with colds, ear infections, and even a bout with pneumonia. Just like you I missed a lot of work, my mother too pitched in and missed a lot of work, so did my husband. He constantly had a cold through the fall and winter months, it seemed like he never was without a runny nose and cough. I spoke to my pediatrician about it because I was concerned that it would never end and I was doing more harm than good. She said that by the time he turned 2 it would get better and by the time he was in school he would be one of the kids that never gets sick. So far she has been right. This past fall and winter were much better with the colds although we did have to deal with GI bugs twice.
My best advice is to try and stick it out. Colds are definately a pain but the socialization and learning situations are definately a PRO to daycare. I realized at one point that I often thought my son felt worse than he actually did. As long as he is fever free, he goes to daycare and I have never had to go get him because he was too sick. Our daycare will call if they feel that they are sick and should be home, and if they have a fever, diarrhea or are vomiting they don't want them to expose the other kids to it, and send them home and want them fever free or diarrhea/vomit free for 24 hours before returning. Does you center have such a policy? If it doesn't maybe switching to a center that does will help decrease their exposure since the center is being proactive about contagious kids. BTW I have a few other Mom friends who's kids are sick as often as my son and they are stay at home kids. Realistically, germs are everywhere and eventually they all get them. Good luck with whatever decision you make. I know how hard it is to have them sick and stress about missing work and just want them feeling well.