I'm curious about the sustainability of mining the currency long term (and thus of the currency itself). Like bitcoin, we don't mine all 21,000,000 coins until ~2140 or so, right? That's a long way off, but isn't it possible that long before then we'll hit a point where monthly mining cost exceeds revenue? That will vary by your local electrical costs of course, and also I'm not even talking about profit necessarily, just a break-even return (via TXN fees and/or a small amount of revenue) such that your electrical costs are covered by your mining operation.
I live in Seattle where electricity is $0.12 per kwh. I plan to continue mining Zcash indefinitely as long as monthly ZEC income is >= electrical cost, which it currently is. But this is easier today because we're in the first mining "epoch" where the block reward is at its highest.
I'm sure this has come up before, but curious to hear people's thoughts around this - wrt ZEC specifically.