Of recent memory....motors i have run and sold....and they are still running great with new owners.
2004 Tohatsu 90 Hp - 1100 saltwater hrs. Flushed zero times
2011 Etec 130 hp - 800 saltwater hrs flushed zero times
2001 Yamaha 150hp - 800 Saltwater hrs flushed zero times
2008 Suzuki 250ss - 300 saltwater hrs flushed zero times.
Personally i dont see the need or benefit. But i do use my boat frequently. I guess if you are one whose boat will sit for a while then it cant hurt.
Stephan, while I normally agree with you, I just had the waterpump/impellor replaced on my Yamaha F150 at 300 hours. I typically just flush with fresh water. It was so gunked up with salt crystallization, I'm amazed that it still had water coming out the pee hole. I'll be using salt away from now on!