eVent is a fabulously breathable fabric, better than any other. To ensure the performance and longevity of your eVent pants, it is really important that you wash them regularly, particularly if you are using them a lot. Build-up of salt from contact with sweaty skin will contaminate the membrane and cause it to start to delaminate, so a good rinse with water is vital.
More information about caring for your eVent garment can be found here.