that after a certain amount of time the bitcoin becomes practically anonymous? As in, not being able to be traced back to the original KYC exchange, or in the case of "tainted" bitcoin, that?
This is an old speculation, and I rather happy to say that this is something I've tried in the past, and like several other users here have said, it's a myth and does not work.
The bitcoin blockchain Explorer is very transparent and there is absolutely no way your coins will just disappear simply because you sent them to different wallets back and forth, except on the account that you employ the services of a mixer, even at this, there are still transaction history visible On your wallet address, but it's just hard to tell exactly where you sent or receive your bitcoins from.