Reusing lock washers

[Flying Scotsman]

Simple question: can lock washers (star type, internal) be reused and if so, how often (what criteria to use to judge when to replace them)?

[jeffmoreau]

My A&P friend taught me to use the internal tooth washer only one.
Toss it out and use a new one each time. Cheap insurance.

[Mel]

"Star" type lock washers tend to get flattened. I recommend using them only once.

[az_gila]

...lock washers should not be used on primary structures (per AC 43.13) and I can't think of any on the RV.

They are specified by Lycoming all over the engine, and Lycoming is very specific NOT to reuse any lock washers.