My Simms guide jacket is about 2 years old now. I've taken super good care of it, and it still repels water as expected. It's due for another gentle washing. Is there really any reason to treat it with anything? I don't see where Simms sells any treatment for their coats. There are a number of products on Amazon like this https://www.amazon.com/Nikwax-TX-Di...0019GOLO0/ref=sr_1_2?keywords=goretex+treatment&qid=1555291996&s=gateway&sr=8-2