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.



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.



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.

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.



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?

I smell bad practice because most online wallets are custodial and that means: not your keys, not your coins.