I hope for you to know the purpose and recovery words for every of your wallets (if those wallets use mnemonic recovery words). Because otherwise it's easy to mess up.
I certainly do hope so and yes, I do have recovery phrases for one of them - the hard wallet. The other one (@bitcoin_wallet as it's mentioned at their X profile) provides only backup files as a recovery meaning.
That is normal and by design to maximise privacy and avoid address reuse. A modern Bitcoin wallet will use any address of that wallet basically only twice without explicit user intervention: first when you receive coins and normally the last time when you send coins from that address.
That's what I got so far.
Normally an address that has been offered to be used to receive funds but didn't receive any funds for whatever reason should not expire. E.g. Electrum would offer such an address again (ok, may actually depend on if a receipt request stays in the list of receipt requests). It doesn't make much sense to keep track of unused addresses in between used ones, so a wallet will and should try to avoid this.
Thanks a lot for such a good hint!
But otherwise as others have said already, you can use previously generated addresses as long and often as you want and it makes sense for you. Keep in mind that address reuse can have privacy issues. When you give someone your address, this someone will be able to see any previously received coins to that address in the blockchain. The blockchain and transactions recorded in it are public.
I just got curious - some of old posters here often put that in a signature and this is not bothering them at all or is it?
There shouldn't be any messing up, but to be sure, it depends on what you actually use. Maybe you want to tell us which specific wallet you use? When you say "login", is your wallet some online wallet?
As it was mentioned above - I use couple of them: software is used for test transactions and as a playground for small amounts. The other one is a hard-based 'Ledger X' and serves as a vault for busyness.
I smell bad practice because most online wallets are custodial and that means: not your keys, not your coins.
Any decent wallet should show the sequence of addresses in that wallet, used and unused addresses.
And they both do so.
By the way - thank you so much Sir for your valuable comments!