The Thinkers: Black holes, black energy and the history of the universe

I've always been of the opinion that human existence will end because of the 2nd law of thermodynamics, through the continual change of various forms of energy into heat. Looks like the black holes are with me on this one.

But I don't really know what that means. Some questions:

How much will the average temperature of the universe increase? Since energy is neither created nor destroyed, there's a finite amount of it in the universe, so there is an absolute maximum (average) temperature, if all of it were converted to heat (Nobody's holding out on us with a _preexisting_ infinite energy source, right? (How would that work? I'm not really sure. But it would definitely obey the no-creation clause they stuck on the universe.))

How long will it take? If it takes even a few billion years, we'll probably have wiped ourselves out. I guess I'm contradicting myself... let me qualify my belief, then. As long as we haven't gotten to us first, then the increasing entropy of the universe will do us in. =P

I think that last one largely depends on universal efficiency, ie the rate of loss-to-heat of various energy conversions. (Sounds like black holes are pretty bad. Converting up to 40% of mass's kinetic energy to heat... talk about heat pollution! (But wait. Heat is kinetic energy on a molecular scale, right? So really that conversion is just large-scale motion to small-scale motion. I guess that's actually a definition of entropy: Conversion of cohesiveness into even distribution. Or random distribution, I should say.)

I think I should stop now. Apologies for rambling. =)