Do intensive language courses work?

Always there are advertisements to learn a language intensively and hence reach your language learning goal more quickly.  But do they work?

My own experience as a language teacher is that if you keep active in your target language through speaking, listening, reading, writing and grammar, your language level will rise regardless of whether you do intensive language courses or not.   

Some people like to study extremely intensively for a number of months and then relax for awhile whilst others like to do little but consistent study but take a longer time period to reach their goal.  There is no one size fits all here.  It is what suits you as a person and what suits your current lifestyle.