I have no experience with the mid weight, but rather the light weight, which I'll offer for what it's worth.

My girlfriend has a kilted skirt from Strathmore in light weight worsted wool tartan. It doesn't get worn too often, but she's had it for several years, it has traveled across the country in her luggage, and it spent nine months "stored" in a pile of clothes (not her fault... it's a long story). The pleats are---somewhat miraculously---still sharp. It *might* have been steamed once, but never re-pressed.