I never give more than 4 stars... I believe 4 stars are/should be considered good enough as "5" stars wouldn't you agree?!
5 stars should be reserved for true masterpieces, or if a woman is givin birth to twins etc. It's like a mentor once explained to me, about the story of the kid who always says the f word all the time. It would stop losing its meaning at one point vs the one person who rarely to never says it, you know that person truly means it the day he says it... makes sense?