Consequentialist ethics would suggest the answer is yes, but in your example perhaps a better result would be getting the same placebo effect benefits from some kind of treatment or remedy that might actually work in itself, beyond placebo. Indulging woo isn't necessary to get positive expectation health benefits.

Knowing about the placebo effect doesn't stop the placebo effect from kicking in.

Anyway, I'd say that there are moments when comforting lies may be worth it, but I don't trust my ability to know when those moments are happening and it would raise my overall believability if I was found out.

I'd say that there are times when it's worth having comforting lies, but you can't figure out when if you're under the effect of comforting lies, so you should follow the strategy of never listening to comforting lies.