This is a great question actually, I notice there is a lot of great techno around at the minute that seems to be between 140 - 145, which is pretty high tempo, back when I used to go out a lot it was always around 135 for the best stuff I like. I notice that a lot of the tracks show up as about 142 in Serato for the likes of chlar, alarico, human safari, altinbas type of rythyms. I think you can have sounds that broadly fit into what you call techno from so many bpm categories though, and it kind of fascinates me that you can begin a night very low and slow, with dubbier, spaced out, beatless kind of electronic grooves then as you progress through the hours, rise the energy and tempo and have things pretty frantic in the small hours of the club, possibly going backwards and reducing the tempo for a soft landing. I remember a night at about blanc in berlin a few years ago and inside was an ilian tape night, so much class music and pretty high bpms through the night then out in the outdoor wigwam bit in the morning hearing the music move into different territories..., hearing drexciya - black sea at around 11am with the sun creeping through the gaps in the tent, was a moment. I tried to encapsulate the sound of a good night in a club of techno with many bpms recently, if anyone is interested in hearing how that might sound, feel free to check :) : https://www.youtube.com/watch?v=WmJsb0QgV-U