Copyright is, in part, to ensure that the creator is reasonably paid for the time the creation took.
No, it's not. This is, no pun intended, patently obvious -- look at all of the unsuccessful artists out there, who will never be successful by virtue of their art even if the copyright lasted a billion years.
Copyright gives people a shot at success, but ensures nothing. Most works are, with regard to copyright-derived income, total flops. Most artists don't get reasonably paid from their copyrights.
It's a lot more like a lottery ticket; lots of people try their luck, and all but a handful lose. The tiny number of big winners, combined with the poor math skills of the average artist or gambler, result in people trying again and again and again, almost always fruitlessly.
But as a side effect, our culture gets enriched with all of this art. Maybe not much, if it's bad, but the only way to get more good art is to have more art created period.
I don't know what the minimum guaranteed copyright term should be, just that 95 years definitely isn't it. Perhaps copyright shouldn't even be one thing, but variable from genre to genre, medium to medium.
I agree that it should vary, probably by medium. Different media have different viable commercial lifetimes, ranging from less than a full day, in the case of a daily newspaper, to usually no more than a couple of decades (and possibly less, now) in the case of TV and movies. On the other hand, I don't think we need guaranteed minimums at all. If an author wants a copyright, let them apply for it -- by as simple a means as possible, but still requiring an affirmative act and the payment of a token sum, such as $1, so that they have to put in at least a little thought. In many cases, the author won't bother, in which case, why should we be putting a copyright on it anyway?