Blindness Potion Effect broken at high time values

So I was working on my adventure map and decided to do a custom potion with blindness, strength III and invisibility all lasting for 100 mil seconds. So I went in MCEdit and made it, but when I went back to test it, blindness instead of actually blinding me it more like cleared the fog, like so: http://imgur.com/a/BD9N7#0

So I though "maybe invisibility doesn't go well with blindness", so I decided to go on and make a new potion where I removed blindness but kept the rest like it was, yet still nothing, so I decided to remove strength too, still nothing. Then I wondered "what if the value for seconds is too high" so I made a new one with blindness 1 that lasts for 100 seconds and it worked. So I was wondering if this is a bug, because all other potion effects seem to work with times like 100 mil seconds.

I went and tested further and discovered any value over 1 mil seconds will make the potion effect not work. I wish to be told if this is intentional or actually a bug, because if it isn't it will be a bit sad for my adventure map.

Note: Since it's a pre-release I am not using any mod, it's 100% vanilla. All I used was MCEdit to edit in the potion, but I highly doubt that's a mod.