I have been using a Klean Kanteen literally everyday for about 15 years. It's just stainless steel with a thick plastic cap and a silicone O-ring for a seal. I think I've replaced the O-ring twice, and I think I'm still on the original cap. I've dropped it numerous times, so there are some light scratches and dents on the bottle and the cap. I put the bottle and cap in the dishwasher occasionally, and the cap doesn't seem to be affected by the dishwasher. I've probably drank several thousand gallons of water out of this bottle.

I tried the sport cap briefly, but I didn't like it. The regular screw cap with a loop on top is the way to go.

Edit: the cap has a 2009 date stamp inside it, so about 14 years