Roughly every 7 years for most of the body, major organs tend to take longer, more like 10. Your brain replaces cells at a way slower rate, you’ll only Theseus your brain about 80% at best if you live a long healthy life.

Taking advantage of you excess resources to manipulate people into give you theirs, is the problem.

Tom Paris tells the Doctor holograms are just light and aren’t real matter, the Doctor turns and slaps Tom.