Block time should be 12 hours instead of 10 minutes

[agorism]

When the block rewards start getting smaller, the total hash-power of the system will go down, and double-spends will become more and more easy to commit.

In order to defend the integrity of bitcoin, we NEED the reward for each block to be worth $10,000 or more.

We have 2 ways to keep rewards high enough
1) like Dogecoin we could continue giving out rewards forever. This would destroy the 21 million upper limit, and hurt the community in a big way.
2) We can decrease the number of block rewards that we give out every day.

My rough estimation says that bitcoin has about 10% annual inflation at current reward rate.
If we only had 1 block per day, inflation would go down to about 0.1% annual.

Litecoin is going to be the convenient to use currency with high inflation, and bitcoin is going to be the less convenient currency with almost no inflation. So we need to reduce inflation to nearly zero.

Eventually, each currency will only have 1 job, and it will do its job very well.

[htimsxela]

With a 12-hour block time it would take a couple of days to receive enough confirmations to ensure a transaction has indeed been accepted by the network. So this obviously is not viable in any way.

[agorism]

Some people purchase government bonds as a 10 YEAR investment.
If your money is not accessible for 5 days, this is not a big issue for many purposes of money.

If you want to spend money on a day-to-day basis, you are better off owning litecoin or dogecoin.
Bitcoin is intended for long term storage of value. It is meant to maintain value for years.

10% inflation is obviously not viable in any way.

[DannyHamilton]

In order to defend the integrity of bitcoin, we NEED the reward for each block to be worth $10,000 or more.

We have 2 ways to keep rewards high enough
1) like Dogecoin we could continue giving out rewards forever. This would destroy the 21 million upper limit, and hurt the community in a big way.
2) We can decrease the number of block rewards that we give out every day.

Or...

The users of bitcoin can pay for the privilege with transaction fees that can be awarded to the miners.  The users can be allowed to voluntarily offer a transaction fee when they build their transaction, and the miner that confirms the transaction in a block will get to keep the fee.  This provides an incentive for miners to choose the transactions that pay the highest fee per byte when deciding which transactions to confirm.  Users will therefore have an incentive to pay a reasonable transaction fee so that they will get their transaction confirmed in the next block.

If a block can hold an average of 4,200 transactions, this means that eventually the average transaction will need to pay a fee of $2.38 to provide the $10,000 per block that you feel is necessary.

We could increase the maximum size of a block such that it can hold an average of 42,000 transactions, and then the average transaction will need to pay a fee of $0.238.

[agorism]

Something like DannyHamilton suggests would be really nice, but I think it is vulnerable to a slow-day attack.

What if there was a block that only 100 people wanted to participate in?
 Then the reward would only be $238, and miners would not be willing to spend $10000 of electricity to win a $238 block.
Miners would switch their computers to other tasks, and we wouldn't have enough hash-power to adequately defend against double-spends. An individual transaction in the block could be worth thousands of bitcoins, and double-spending it could be catastrophic.

How can we be sure that there will be 4,200 transactions every 10 minutes forever?
If there is ever a gap, then bitcoin becomes vulnerable.

Paying to keep bitcoin safe 144 times a day is too expensive.
Only protecting bitcoin once per day would be way cheaper.

[Phrenico]

OP, a much more reasonable suggestion would be to change the reward to 6.25 BTC or less but maintain that reward for ~8x as long. Ten-minute blocks provides adequate security in a reasonable amount of time.