Thrashed it (within reason) for bout 200 mi. in the mountains
If I was only living in a place where DIY and hardware stores were really DIY and hardware stores, I wouldn't order evey bolt I need overseas from eBay. Trust me on that one brother...Drain bolt washers are typically a soft metal that has two functions, both to seal and to lock the bolt. On the first use they will work harden even if the dimensions don’t change much. Copper ones are easy to anneal, but they (just like the aluminum ones) are so cheap that I’ve always wondered why bother.
All that being said, I know that a lot of people keep using the same washer for the life of the vehicle with no problems.