How often do you look up words ?

Some look up everything they don't understand whilst others only do it if they cant understand what's going on. I find the former very tedious

When reading in my native language I understand almost everything, I only look up when the word is somehow interesting or it has appeared more than once in a few pages and I don't know its exact meaning.

In English I only look it up if the word has been mentioned later and my interpretation somehow doesn't fit or it doesn't make sense.