Or just do 40 hours of work every week. If you cut out some of the time-wasting employees have to endure you might be able to get the work done in that amount of time anyway.

surely you have your own additional "timewasting" when it comes to looking for opportunities, convincing employers you actually have the skills to do the job, dealing with corporate departments who think you should be filling in the same paperwork as the regular employees do at the start of their employment for each individual project (the only part you might actually be able to say no to...) and managing your own accounts.

You don't bill for that stuff, though.

If not, then you're not managing expectations well, or the organization your working for is just a sweatshop anyway.