Do not spend unnecessary time on a cell phone - you must supervise your dog at all times and be able to give your dog your full attention. (neworleanscitypark.com)
It's unlikely you'll manage to change someone like this, so don't waste unnecessary time on him or her. (blog.completelyfreedating.com)
You will spend a lot of unnecessary time on information that you don't need or already know. (careerdirectors.com)