"A cleanup cycle where old blocks are consolidated and discarded" Already implemented by multiple clients, and already envisioned by Satoshi in 2008. See Simpl

"A cleanup cycle where old blocks are consolidated and discarded" Already implemented by multiple clients, and already envisioned by Satoshi in 2008. See Simplified Payment Verification (SPV): https://en.bitcoin.it/wiki/Thin_Client_Security#Header-Only_Clients https://en.bitcoin.it/wiki/Thin_Client_Security#Header-Only_... (wiki page out-of-date - this is an incomplete list of clients.) The storage requirements of an SPV client only grow by 4MB/year regardless of how many transactions the global network processes. See section 7 of https://bitcoin.org/bitcoin.pdf https://bitcoin.org/bitcoin.pdf "Miners will not continue to mine just for fees" Yes they will. Most of the observed mining power continued mining through the first reward halving of Nov 2012. This is because miners have different operating costs. So the few that stopped mining actually caused a small difficulty drop (~10% IIRC), which made it a bit more profitable for those who continued mining, so the network stabilized at a slightly lower hashrate (before it continued increasing again in Jan-Feb 2013.) This demonstrates that mining is an economically self-adjusting activity that can survive 50% drops in mining income. And the disappearance of the fixed reward in year ~2140 will NOT be an event where more than 50% of your mining income disappear overnight [2] so Bitcoin mining is economically viable forever, theoretically. [1] https://en.bitcoin.it/wiki/Controlled_supply https://en.bitcoin.it/wiki/Controlled_supply [2] Fees currently average ~0.05 BTC/block. The fixed reward is 25 BTC/block today and decreases smoothly by halving every ~4 years, therefore it should reach 0.04882812 BTC by year ~2048 [1]. This means even assuming fees never grow beyond 0.05 BTC/block (eg. Bitcoin's adoption stagnates), fees will already represent most of a miner's income by year 2048. Subsequent reward halvings (0.04882812 BTC to 0.02441406 BTC in year ~2052, etc) will be insignificant compared to the income from fees. And the disappearance of fixed rewards in year 2140 will be an even less significant event. Fees will have already represented the majority of mining income for the previous ~100 years.