I can't fathom ever getting bored with coding so to me, answering this question is an NP-Complete problem for suuuuurrrreeeee.
I do get "sick" of coding sometimes... And that occurs when I've done it enough for the day. E.G. if I'm doing hardcore coding for like 6-8 hrs then I'm done and I want to do other things the rest of the day more than likely. Doing those other things helps rejuvenate and motivate me for the next day.