Depends how much abuse it has seen. 5/6 years seems like a pretty reasonable amount of life to ask out of a component though. Get a new one if you are worried about it, $40-$80 isnt alot of money to keep you from smashing face first.
Kind of what I thought. I am only 68kgs and my riding level is fairly tame compared to some folks so I could probably keep running it. I think the E13 one is supposed to be pretty robust? I might change it for the hell of it - I found some burgtec ones cheapish so it might just be an excuse!
Pull it off of the fork and take off the bars. Inspect it for stress cracks. Can't recall if the E13 was painted or ano (guessing ano) but if ano, should be visible. None? Slap it back on.
The only stem that I have ever "broken" was a Thomson X4.... and that was a crack that developed on the faceplate near one of the bolts. Cause? Probably the ham fisted wrench that installed it and overtorqued the bolt. (Me)