We have transactions fees, to avoid creating tons of transactions and increase the blockchain size to a extreme amount.
Those transactions fees are sent to the next user who is the miner.
How would the economy of a coin would change if instead of sending the transaction fee to be mined, the transaction fee was frozen and 1 year after it it would be sent back to the wallet. The user wont lose that money, but still can't keep making tons and tons of transactions to spam the blockchain.
The transaction fees are the part that should ensure Bitcoin run forever. The block rewards are decreasing, rather sharply. When those will become really small, the miner have to be paid somehow for their work. That's what the transaction are fees for, not only to avoid network spam.
This being said, if your idea would be implemented, in some (many?) years from now, there's a (good) chance the miners will leave.
Yes, I forgot about that obvious part. It would require changing the system.
Some examples of those changes would be:
A=
1-Has frozen transaction fee going back to you after 1 year.
2-You can also send coin to some place.
3-Money sent to this place back as reward after X months.
4-Amount of money sent to this place is your stake used to decide the mining.
B=
1-Has frozen transaction fee going back to you after 1 year.
2-You can also send coin to some place.
3-Money sent to this place back as reward after X months.
4-Amount of money at this place is your stake used to decide the mining.
C=
1-Has frozen transaction fee going back to you after 1 year.
2-You can also send coin to some place.
3-Money sent to this place back as reward after X months.
4-Amount of money sent send as reward from this place is your stake used to decide the mining.
D=
1-Like A but instead of X months, the money go back as miner reward at next block.
E, F, G, H =
1-Like previous 4, but instead of sending coins to some place that will go back as reward after X months (or next block at the case of D), while making a transaction you can choose between making a normal transaction fee that will go back to you after 1 year, or sending it to some place where the fee will stay there and will go back to as reward to miners and also be used to do the staking related things.
There is some one change that wouldn't have the freezing method.
I=
1-All transactions fees go to the reward pot, there is no freezing.
2-What is used to decide the miner is the amount of coins send as transactions fees.
At idea I you will lose your transaction fees like happens right now, but they will have an extra use.