It seems there can be too much of a good thing. Donald Trump's corporate schmoozefest The Apprentice has lost nearly 4 million viewers since last season, thanks to an overall drop in reality ratings and, yes, that other Apprentice with Martha Stewart, which musters only 6.7 million to Trump's 10.3 million. ''Wednesday and Thursday split the audience,'' admits Mark Burnett, who exec-produces both versions. Burnett says Stewart ''doesn't have time'' to do prime time beyond this one-season experiment (not that anyone was asking, given the ratings), but Trump's side of the franchise lives on: He's already shooting season 5 (set to air this spring). And he claims stuffing four contestants into the taxi of shame on the Oct. 27 episode doesn't signal that NBC has cut back on the number of episodes; there are always more contestants than episodes Trump's trigger finger simply itched sooner rather than later. ''They happened to perform really badly on that task,'' he explains.