My original plan was to stay 3 years at my first company, and then change jobs for a raise. I ended up staying 5 because they gave me great raises for the first 3... And then screwed me on 2 years, at which point I knew I should have left at 3 after all.

After that it gets murkier, but in general if you aren't seeing really nice pay raises every 3 years, you can get it by changing companies.