How often should I lube my chain?

Unfortunately, this is a little bit of a "How long is a piece of string question because it depends on the conditions in which the chain is used. For instance, if you are riding in the rain a lot, the chain will need Wet road conditions, or very hot and dry weather both 

However, if you force me to answer, I'd say every:

When should I oil my chain?

Some lubricant makers recommend sometimes recommend to leave the bike for a couple of hours, or even overnight, before riding again. This gives the lubricant time to spread into the tiny gaps in the chain bearings. 

This is a good idea if you can discipline yourself to apply the chain lube after the ride. 

However, for the most part ...... "Ain't nobody go time for that!"