2.2 y.o. DS has had a rough week and a half - first slapped cheek disease, then a really, really bad cold (maybe two colds in a row as he had a day or two in between when it wasn't so bad).
He is very tired and is sleeping much more than usual. I wasn't surprised at first, but the tiredness has gone on for about 10 days now, even though the cold symptoms are going.
The only other thing I can think of which might be affecting it is that we started giving him gluten again after a fortnight's gluten free trial. He's not getting much exercise or stimulation at the moment.
Once he's awake, he's normally 'reset' to awake for 6 hours after waking in the morning, and for 6 hours after a 1.5 hour nap (longer if he naps for longer, shorter if he naps for shorter). Now he's napping after only 3.5-4 hours awake, napping for 2.5-3.5 hours instead of 1.5, and then sleepy again after only 5 hours. He's probably sleeping between 2 and 3 hours per 24 more than normal.
We have had a few nights when he's been up for 1.5 hours in the night, but normally that doesn't have any effect on how much he sleeps the rest of the time. And he seems to need all that extra sleep even after good nights. 
Is it normal for illness-related tiredness to continue so long?