If rev projections how would you calculate it?
A company with one Avalon running at 60GH/s would probably show how much they're making per day / week at the current difficulty, subtract any expenses (such as electricity, hardware costs, and "Management Fees"), and then distribute the remainder to all investors.
That said, valuing a company really comes down to how much the company takes away in fees / other expenses, how they've structured their dividend payments, and how much equipment they have.
Revenue projections come down to figuring out how much you're making at the current difficulty, and then figuring it out again as the difficulty increases. There's no surefire way to know what the difficulty will be, but it helps to try and make a prediction. What I've done in the past is to figure out how many preorders there were for all ASIC companies, and compare that to statistical data I pulled from the top pools (essentially getting an idea of who the "hardcore" miners were). It's even more difficult to make these predictions now that ASICs are starting to mine...compared to when it was just GPUs and FPGAs.
Typically no, since the "mining" company isn't "mining". And a 3 month investment is really not long at all in the big picture