For a kitchen sink shut-off valve, or any sink for that matter, does anybody know a good reason to use valves that are "sweat on" as opposed to the kind that are just threaded? I'm getting tired of those valves that just sit there unused for years and when you finally need them to work they no longer seat properly and just leak. I would prefer to just unscrew the old one and put on a new one when needed - unless there is some mystical plumbing code or reason to use sweat on valves only. Thanks.