I've been using a ~2L platypus mountain biking and hiking for years. Wore one out, and felt that after a couple hundred rides I shouldn't bother them about the lifetime guarantee.

My experience is that if you only use water, rinse and drain within 24 hours, you're golden.

I've gotten one slightly funky and been ok with a strong salt water wash.

I got one funkier than that and had to use dish soap, and then the salt water.

Other than that, it's my ritual to suck and spit three times at the start of a ride or hike. If there's a plastic taste, that's when I taste it.