i went ahead and added the max days where coins are profitable. (usd/day > power cost/day)
this is an estimation of course since the rate of btc can do anything during the calculated time frame
it also show the estimated difficulty before coins are no longer being made.

I have been thinking about adding in a section to add hardware after a threshold. like say you want to add asicminer blades once you make enough coin to buy one. so at current price (4btc) after 4 btc has been generated, reduce total btc by 4 and add 10GHs to the hashing power.
so you would have a coin threshold and an associated hashing power increase as well as power rate increase.

is this something that would be meaningful to anyone other than myself? the intricacies of this would be something I would have to play with and would throw off other calculations like the max time hashing is effective but could offer some insight to how best to expand your mining setup.