I've found a bug that can be re-produced regularly. When doing the mage quest to cleanse the focal points in Winterhold the fortify magika buffs never disappear thus giving you unlimited magika. Still trying to find a fix.

The buff does eventually disappear for me, but it does take quite a while...

I thought it was intended, like that 24 hour buff (for something else) you get for doing the 7000 step pilgrimage...

Yeah they seem to have dispelled as well. They are just lasting much longer then the duration states I believe.

So does this really dissapear after a while? Confirmed?

Yes, it goes away after a while. It may be 24-48 (in-game) hours, but it does expire on its own.