Generally crush washers will last a few oil changes. My subaru is the same way. Since they are so cheap it is easier for them to tell you to replace it every time to avoid leaks. Every time you torque the bolt down to 29ft-lbs (ft/lbs is a rate, not a torque) it does crush a bit more...but most people wouldn't be able to tell you 29ft-lbs from 75ft-lbs and they just tighten it enough so that they think it won't leak (which is usually a lot more than 29 ft-lbs). Some companies used to use nylon or fiber type washers, but people still would overtorque them and split the washers.

Like you mentioned, torque wrenches are a mechanics friend. Another good place for them is Lug nuts...because I don't know how many cars I've had to work on where the lugs were on so tight I needed a big breaker bar to get them off, not so good to put that much stress on your wheel studs.

 

Thanks greenandblue, I might just do it next time....

 

My 06 HCH finally asked me to change the oil today. I'm at 15% oil life and 7456 miles. The interesting thing is that the 7456 miles = 12000 KMs. So the oil life calculation is based on KMs. Kinda cool.