It runs weekly on MeTV. I think it was in the third season when I started watching, then it started back at the beginning. I just watched 1-26 - "The Amphibians". It was actually quite good, even believable.
I agree with you about the two shows. Later episodes it was more like a creature-of-the-week comedy and for some reason there were sparks flying in the control room EVERY episode! That is very comical.
But during the first season most of the shows seemed thoughtfully written with a combination of intrigue, drama, and believable sci-fi, with a touch of kitsch thrown in for good measure.

anybody who's watched all 4 seasons can see that there are really two VTTBOTS series.
The first which runs through season 1 and most of season 2, is a serious tense action thriller with a little bit of sci fi and fantasy.
From there on in it's just bonkers and makes no logical sense whatsoever.
It's almost like the production team dropped acid halfway through season 2. - nashspacerocket
I never watched VTTBOTS until the DVDs were released. I bought Season 1, Part 1, as a lark and enjoyed it enough to buy Season 1, Part 2. As you say, Season 1 was a well made spy/sci-fi series.
I later watched all of Season 2 (here on the IMDb for free) and even that early the decline in quality was evident. However, there were a few great episodes, i.e., "And 5 Of Us Are Left" "Killers of the Deep" and two "Phantom" shows.
I've seen a little of Season 3, and so far the only standout episode has been "The Day The World Ended." I have yet to see any Season 4 episodes.
I suspect the fact that a new series got added to Irwin Allen's workload every year of VTTBOTS' run had a lot to do with the decline in quality. The man seemed to be more interested in launching new series than maintaining the quality of old ones.