2005 stratus sxt misfire

wife has a 2005 stratus sxt 2.4 dohc(X). It keeps blowing a code for misfire in cylinder 1 I changed the plugs and wires fixed the problem for about a month or two. The other day she told me it came back so i went up to were she works pulled the plugs again and its the same thing all the plugs look pretty much the same cylinder one is slightly lighter in color but thats from the misfire. But when she took it to work this morning it was fine engine light was off and ran fine. She also said it only does it for a short while then it stops. Can anyone help or give advice on this issue the cars only got 46k on it. And i don't have the time to keep chasing my tail if you know what I mean I'm working 10hr days 7 days a week any help would be great. Thanks Ryan