If this is your preferred mode of use for your SmartCharger most of the times, then you’re probably better off using a standard charger. This is because you’ll just keep the power bank battery at 100% ALL THE TIMES, which is not good for the power bank battery at all (like @jim_lewis has pointed out to you above). The power bank battery will probably die within 3 years in that situation.
Then the question becomes whether you can still charge your aids via the SmartCharger plugged in despite its power bank battery already dead. I vaguely remember that perhaps this is the situation @SpudGunner asked about which I might have done an analysis on.
If you still want to own a SmartCharger instead for the few times when you travel or maybe for when you lose power supply at your home and can’t charge your aids, then an alternative is to switch from a wall outlet to a third-party power bank (like @SpudGunner 's setup with his standard charger). Otherwise, in the first year or year and a half, while the SmartCharger’s own power bank has not deteriorating too much yet (due to being kept at 100% all the times), maybe it’ll work for you. But the next year or two may prove to be the unreliable years for you.
If you’re going to own a SmartCharger, you don’t have to “co-charge” if you don’t want to. But you should charge the aids with the SmartCharger unplugged every 2 nights if you have 3 LED dots on it (fully charged battery). Then when there’s only 1 LED left, charge the power bank up to full first, then repeat the cycle.