Make more of them per year! Well, just one more to be precise.
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The best time for Trials, in my opinion, was in 2017 - we got a new Trial in Morrowind, and a smaller mini-Trial in the Clockwork City DLC. Two Trials in one year! It was glorious.
It hasn't happened since then though. I'll give Murkmire a pass since it did come with Blackrose (arenas are nice too), but I'd like to see the double-feature Trials happen more often.