Carrying out a sunnah action without making the intention

An act that's sunnah. When one started it, it was done with the niyyah of sunnah. After years you become accustomed to it, it becomes a habit like dusting the bed or reading certain duaas or eating with the right hand, etc. Will you still get the thawaab of practicing a sunnnah or will the niyyah be have to made every time you do an action? Some aalima said that one won't get rewarded without the intention.