C has had a cold for 7 days now. It started with a mild cough/sneezing, and then he became very congested, with a croupy cough at night (lasted for 2 days). Now the nasty cough is gone and he doesn't sound as congested at night, but he's still coughing/sneezing with green snot (sorry).

He doesn't have a fever, and hasn't had one this entire time. If he's not considerably better by tomorrow, I'm going to take him into the pediatrician, because I worry about it becoming an infection. How long do your LO's colds last? When do you take them to the doctor, versus riding it out at home?

ETA: He's 8 months.