How long should implantation cramping last?

Well, it all depends on the person. Some people say only a few hours to a day. Others may say it's impossible for it to last longer than that, but speaking from personal experience that is bogus - mine lasted almost one week! Mine weren't painful. They just felt like I was about to get my period (heaviness, bloated, etc...) Some women claim that they are a bit painful. And then again, a lot of women NEVER even have implantation cramps. And sometimes with implantation (cramps or no cramps) you get implantation bleeding, which should be much lighter than your period and only last a few days. I never got this type fo bleeding, but many women do so don't worry if it happens.