Most of my taping "adventures" average around three hours. Before each time I go out, I throw two new batteries into my nbox, moving the "every show" batts. into the "every other show" batts. position. I'm only going through two batteries an adventure; therefore, I really have no complaints about my nbox's battery consumption. When I first started, I was unhappy because I was using rechargeables.
Using the rechargeables in the manner you suggested, Nic, would work fine . . . . just seems like it'd be more of a hassle than it is worth. And I've got them sitting right here. I'd still be putting in two new batteries at a time and I don't really see where you'd be saving anything.