How long?

How long can one illness last? Dominic is still sick. Temperature tonight was as high as 101. He's still coughing a lot. He's also sleeping a lot. This afternoon after I picked him up from Dave's he actually told me how tired he was. This from a child who hasn't regularly napped since at least the summer! He napped this afternoon and still fell asleep around 7pm. Thankfully he ate a little bit more today but still not as much as he should. Assuming the fever is still there tomorrow I'll be calling the pediatrician again.