It is ideal to keep your temps as constant as possible, but a lot of times it's easier said than done without a good fermentation chamber. As long as you stay in the given range you should be ok, but most importantly don't let it get too hot. That's much worse than a little too cool, IMO. I'm willing to bet the actual temps inside your fermentor are more stable than you think.
Bottled: Blackberry Mead
On Deck: Pilsener, Brown, Barleywine, Coffee Porter