A lot of myths exist on PE (premature ejaculation)
And as said earlier, 5 min. is not bad, but tel this to your wife if she is not getting satisfied.
But indeed, normaly we speak of PE when it lasts less then 1 min.
And treatments can range from any type of exercise, to herbs, medication or psychology. It depends on whom you seek advice at.
at
http://prematureejaculation.sohosted.com you can find a summary of different treatments for PE.
Also be clear, you can find a lot on internet, but until now no proven 'cure' for PE. But one can improve one's condition...
Regards