Qtum wallets manage a large number (up to 100) addresses and opportunistically top them up in the keypool. The default behavior for the wallet is for single-use addresses, and if you are sending QTUM the wallet will actually select a larger previous transaction (this is the UTXO model) to send, along with a new “change address”, which will receive the change back from that transaction on this change address. Wallets sending out many transactions (but not for staking) will burn through these change addresses and they should have their wallet.dat file backed up again after about 50 transactions (the keypool is for 100 addresses). If you are only (or mostly) staking, it would be good practice to backup the wallet.dat file again right before every version update (so at least every few months).
As for learning more about this topic, I suggest Googling for “bitcoin keypool”. There is lots of good info in the bitcoin wiki and in the Bitcoin Forum, and it mostly applies directly to Qtum since this basic functionality was forked from bitcoin code.
You can use the command "listaddressgroupings" to see which addresses are holding QTUM in your wallet, but you don't have to move them around, the wallet will sum all the addresses for the staking wallet weight.
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