I enjoyed the series, which regretably only lasted one season. I now have the series on DVD, and I also have most all of Irwin Allen's 1960s SF series.
Back in the 1970s I had the opportunity to meet L. B. Abbott who was the former head of special effects at Twentieth Century Fox Studios, and who worked on all of Allen's SF series. His stories of the behind-the-scenes stuff, and how they did the effects, such as the colorful time trave effects that had the two scientists seemingly falling through a colorful "time vortex" were fascinating. Mr. Abbott did a lot of good creative work on a low budget --- yet The Time Tunnel cost a LOT of $$$$ in the mid 1960s.