I got a 600D (canon) few wks back. Within a week it started have dead pixels so the shop is willing to replace a new one for me. We tested in the shop, the 2nd one no good: dead pixels appears immediately. We then tested the 3rd one. Couldnt see any in the shop but it appears when Im home.
So I bring it back. They tested and agree (1 pixel but it looks like a star on the screen) and got my 4th one today. We tested a bit longer this time no dead pixels.
I am testing the cam now and the LCD screen have a red dot pixel now (looks like a special star at night).... If you were me will you bring it back again or just leave it..?
You say you "tested a bit longer"...how are you testing? Sounds like hot pixels, not dead pixels. Hot pixels are always there in every camera when taking long exposures. Dead pixels are something altogether different. If you are testing by taking long exposure shots with a lens cap on you are seeing normal camera behaviour.
Not sure about 600D but some models can create a dead pixel map as part of their firmware. There are tricks to get it to update so it removes these dead pixels. You'd have to ask Canon owners at DPreview about if and how to do this. For example a recent thead about Nikon D800 mentioned by clicking on the remove dust twice it updated its dead pixel map. So perhaps there is something similar with the Canon.
i've got a 600d and haven't had any problems, sorry that you have. following on from what greg said, you might want to try downloading magic lantern to your card, that might override the firmware... and give you more control over the camera.