While traces of whips and the like take usually less than a week with me (on the rare occasion that I receive any traces, as my Dom is so proud of leaving no traces *sighs*), I got a rather intense caning last year in September. While the original dark bruises healed rather fast, dark shadows of them remained for close to 4 months.
I never experiences traces like this before (and no, the skin was not ruptured or broken!).

I guess I will keep my mouth shut instead of begging for bruises for the next, lenghty period of time. *winces at the memory*