Eee...memory in a human doesn't work the same as memory in a computer (which your sortof illustrated with your car keys example).

It's not like your brain just deletes entire memories; your brain simply does not work that way.

You'd never have a second first kiss, or a second time learning how to ride a bike, or a time when you got to fall in love with your wife again...you wouldn't forget about having kids, and get to experience raising them again.

Just as exploring the river-bed near my childhood home isn't exciting to me anymore (sadly), you'd have to be continually seeking out new experiences in order to get that positive you're-doing-something-new feedback from your brain.