Yes. If you're not absolutely careless they can last you up to 5 years easily, average is around 3 years I'd say. $200 over that period isn't much and once you get spoiled you can never go back. Performance increase isn't that huge as people think, but comfort and quality materials are worth it.
Personally, I am happy with a standard keyboard. But a gaming mouse or even a mouse with a few extra buttons is very helpful if it helps my left hand from doing crazy stretches to hit some of those further way buttons.
Any keyboard with n-key rollover is a good thing. Mice? More a comfort thing. I use a 4 button mouse that pretends to be a gaming mouse, but really isn't. Has adjustable DPI and extra buttons, though, and I quite like it. Looks kinda like a Death Adder, but it's a tad smaller. I found my friend's deathadder clumsy and uncomfortable when trying to use it after being so used to my mouse.
And before that I used a Wheel Mouse Optical, which was a favorite for a long time in the Counter Strike scene because they work pretty much forever and have a low dpi. Good for the big, sweeping movements they favor.
One day, when I am too old for adventuring, I will settle down and open up a little armor shop called, "Victorious Secret."
I would say that for gaming a mouse can really be worth it. Even for a casual gamer, a really crappy sensor can impact gameplay.
I feel that keyboards are more about typing. I personally think you do not really need them for gaming and even if you do get them, it is not because of any real world benefit, but more about how they feel. That said, there are some features, like key rollover, that are kind of a big deal.
I5 3570 | GTX 760 | Kingston V300 120 GB | Corsair VX550 | Asus Xonar DGX | Corsair 300r | AKG k550 | Matias Mini Quiet Pro | Zowie EC1 Evo White