Time travel can be like that, particularly in episodic TV series. This is a typical example: one writer has a story that involves Herb hitting the reset button so Lois doesn't find out about Clark's dual ID before she's "supposed" to, but other writers who use the same characters and events don't ensure that their stories are consistent with the first, and no story editor calls them on it -- if they even care. Remember the old Hollywood saying: "I don't want it good, I want it Tuesday!"
Herb's questionable decisions can be doubletalked around: he does what he does because that's the way history says it happened, and he wants to preserve Utopia. That can be argued against, of course, but at least it explains what's going on -- after a fashion -- and is very reminiscent of the Silver Age comics' method of dealing with time travel, namely that history, past or future cannot be changed.
I don't agree that Herb erasing L&C's memories was pointless. He knew that Lois was going to find out, but when she found out and how she reacted were the important points. If the future can be changed by a time traveller, then it is quite possible that the timestream is chaotic -- a smal change, such as Lois finding out too soon (before she's close enough to Clark, for instance) could lead to massive changes in the future, so from Herb's p.o.v., the fewer and smaller changes, the better!
Of course, if he's going around erasing memories, why not do Tempus before dumping him in prison in 1866?
