once. I don't subscribe to the idea of taking off my chain to soak it in solvent and then lubing again. first, it probably wears the chain more since you remove the lube from the pins where it actually is needed. And even if it would be good, just not worth my time and the cost for solvent and lube.

I wipe off my chain after each ride with a shop towel. Every once a while put some oil on it. Replace at 0.5% elongation (measured with steel ruler).