IF you change your oil regularly (3,000 miles), and IF your oil level is full all the time, and IF you hit the clutch the very SECOND you peg the tach, you won't do any serious damge. However, DO NOT make it a habit! So long as you shift right at red line or before, you should have no problems. It also depends on how old your car is. If it's new (less than 100,000), the compression, seals, and valves are probably in perfect tolerances. As it gets older, those things will inevitably wear out, and I wouldn't go burning things up with 150,000 miles on the engine. Even if it still runs great.