just leaving a PSA here, also, @Takebacker; because he'll probably like this info.
i had an overall with +1 second invincibility on it, i checked the difference in time between overall and no overall, the results were pretty cool already, with me having a very nice timeframe receiving no damage at all.
afterwards, i mounted a +2 second invincibility nebulite on it, the time increased, from what i see, they seem to stack in time, but i haven't ran any real testing but getting bumped a few times, the increase does seem bigger though.
i went and also tested that theory that if you get super-KB'd, you'll be stuck for as long as your invincibility lasts, this proved true at castle golems
so yea, just leaving the PSA here, i only have +3 second invincibility on me and am already loving this, if you have stance i greatly recommend it (or at least a B +1 sec nebulite) over damage.