Mark-
In my experience, the charging circuit that is in any consumer device (scanner, h/t, cordless phone, all of them) is simply a dumb "overnight" charger. They pretty much all charge at a 1/10th "C" charge rate, and they also are cleverly supplied with commercial AA cells that are built for robustness. They are typically only 600mA capacity but built to withstand constant charging AND abuse, in terms of overcharging and being allowed to go dead. These are intentional qualities and the reason that "obsolete" 600mA NiCd AA cells are still so popular among manufacturers. It is damned hard to kill them.
Since the charging circuit and the batteries are matched at a 1/10th "C" charge rate, and the batteries are designed to take that charging rate "forever" without damage, they can be charged perfectly well in the radio by just leaving them overnight, i.e. 12 hours for a full charge even when they were totally discharged going in.
As to overcharing damage? Consider the average cordless phone, which sits in a charger base 24x7x365 and still gets 5-10 years on a set of batteries. I've got a handheld radio that stays plugged into the AC charger (the radio has an internal charge controller set at 1/10th "C") pretty much all the time as well--and has done so for over a decade without any problems, just the usual slow battery capacity loss.
Yes, an intelligent outboard charger which monitors each battery will charge them faster. And might be "better" in some other way. But is it worth the eventual damage to the battery cover, springs, contacts, or just the nuisance time? Probably not unless you MUST have that faster charge.
Battery charger engineering is really old-school and mundane in these devices. And very intentionally optimized so you really don't have to think about it, and really can't kill it.
The real worry should be the wall-wart for the charger (any charger) itself. Fire departments all over the world will be glad to tell you about the incredibly large number of home fires that are caused by wall warts, even the UL/CE certified ones.