"If the award lowers over time" makes it sound like, you still entertaining other concepts besides adjusting awards & difficulty towards Koomey's law? Are you considering another alternative.
Well, I'm still speculating here. I don't have anything set in stone.
We can't assume koomey's law will hold, so we have to let the market figure it out.
To account for Moore's Law, I believe the difficulty should adjust every 25k coins (up for debate) based on coin-hours. Coin-hours = # of users in a block * # hours between blocks. Though I haven't released proposal 4.0 obviously, this can be determined correctly based on the way my new design for freenets/corenets will work. People won't be able to just join or leave willy-nilly.
Then, to account for Koomey's Law, the award will adjust every 250k coins (up for debate). How the award will adjust I'm not sure yet. It can't be from 6->3 because that will just bring in the reign of FPGAs and kill GPUs. So I'm thinking from 6->4.5->3->6 or 6->5->4->3->6 (probably this). If it goes too fast, we are likely to give low wattage high efficiency miners an even bigger advantage by making GPUs totally unprofitable way before their time--thus killing the supply and causing a permanent increase in the CTP before its time. So "on occasion" is sort of referring to the fact that when
it happens is not very predictable. "if it lowers over time" is just me speculating on how this scenario would work.
Perhaps # of coins shouldn't be the only factor though, because if ENC explodes in popularity, 250k coins could go pretty fast. Then again, I dunno, because people might just be mining like mad because the CTP is much lower than 1 ENC. So perhaps it has to stay rigid. Then again, perhaps the change in award could be based on how long it took to get there.
All this is assuming that the difficulty never goes down which I think needs to be part of the plan. Difficulty is based on coin-hours, not amount of computing power, so I really don't think it should be an issue unless someone is trying to grief the system or intentionally make coins cost more to produce so their existing hoard is worth more. To do it will cost them a lot of money, but I'm trying to think of the far-future.