So, that "single permanent address" can work fine if you're just looking for donations, or doing transactions with people you trust.
If you're doing any kind of transactions in volume, it's much easier to just give each customer a unique address to send to, so you can verify that you've been paid when the right amount has been transferred to that address. That way you don't have any confusion of who has actually paid you if two people owe you similar amounts at the same time, and you see a transaction come in of that amount.
So yes, it's possible to pick one address as your "single permanent address", but it's not something that's expected or common.
If you're doing any kind of transactions in volume, it's much easier to just give each customer a unique address to send to, so you can verify that you've been paid when the right amount has been transferred to that address. That way you don't have any confusion of who has actually paid you if two people owe you similar amounts at the same time, and you see a transaction come in of that amount.
So yes, it's possible to pick one address as your "single permanent address", but it's not something that's expected or common.