I've been using Grout Perfect for 4 years and that job that Mike did will last for a LOOOOOONG time.
If you get the grout clean and there is nothing on it (wax,mop&glow,etc) it will last (don't want to use the word forever) The problem is people don't get the gorut clean or know how to test for problems and try to color seal anyway then your right it comes off and looks like crap.
Nice Job Mike!