This is nothing at all like the emissions debate.
As far as technical reasons, will increasing the blocktime and thereby decreasing the # of blocks reduce the size of the blockchain to any meaningful degree?
It might. The prevalence of zero transaction blocks is mainly filling the blockchain now. In the future, who knows. So, if we might see a decrease in size of blockchain if transaction levels continue as they are, but hopefully we see more transactions, not less. So I don't think this rationale has weight.
I'm with ArcticMine re: tabling this issue until later.
However, I do see the rationale in decreasing orphan rate, even though I am not entirely aware of the negative consequences of orphan blocks - I just get the gist that they are not ideal.
Thus, I would be fine with a 2 minute blocktime. I did some digging into the original TFT bitmonero thread, and indeed this is an old issue. Back then, the compromise / rationalization was 1 min blocktimes during the solo mining phase, and then 2 minute blocktimes later.
I believe "tabling for later" will just result in status quo forever. It won't get easier to change. We say we are young, nimble, able to make the changes we want without all the politics of BTC. Are we?
This change, being trivial technically, is all about discussion, and talk is cheap anyway. I don't see how discussing it in this thread (by mostly non-developers - at least of Monero) will have any measurable impact WRT slowing down the achievement of the design goals.
Orphans are wasted hashrate; they make the network less secure than it would be without them. They can also cause "false" confirms that are reorged out later. Bigger blocks (more transactions) would make the problem worse.
Also, combining a slow-to-verify POW with a 60 second blocktime results in a nice little advantage for large pools (even without any malice on their part).
Is blockchain size even still relevant when moved to DB ?
Absolutely.
