My thought is that, the reason for this rule is for privacy concerns, but then, I might be wrong, so my question is "are there or is there any security issue(s) related to using or reusing a particular or one single bitcoin wallet address for a very long period of time?
Just for privacy reasons.
But some people are still using different addresses for different transactions but in a way many of their addresses can be tracked. An example is a person that receives 5 transactions, making it 5 inputs, spending the whole coins with 5 inputs in a single transaction, this will be easily known on blockchain explorer that the whole 5 addresses belong to the same wallet.
Another issue are that people are making use of light clients (SPV wallets), this type of wallet depends on central server(s) as they are not running full node. Central servers can connect many addresses generated by the same wallet together and linked it to their IP addresses.
For privacy, the best is to run full node like on Bitcoin Core or having your own Electrum server.
But if you make use of wallets like Electrum and be spending a specific inputs using coin control can be of help because you are still having privacy to an extent to many people as your addresses are not connected on blockchain but only to central servers if you are using light clients. But to have complete privacy run full node using Tor connection.