Interesting topic. I've owned my Adams E1 for three years, and in that entire time, intonation was within adjustment. Until the last week, that is. I'm attending the Brass Chamber Music Workshop (BCMW), where we play all day and into the night (5 45 min. practice sessions, a concert piece, and 1-2 hours of freelancing each evening). My intonation became progressively sharper as the week went on, to the point where there was no adjustment left. It took a good 15 min. of playing to bring the horn in tune. I experienced some other changes in embouchure at the same time: I gained considerable endurance, but my tone quality suffered. I'll be playing tuba this week, so my expectation is that my Euph embouchure will return to normal.
San Jose Wind Symphony (on leave 2020)
San Francisco Brass Band
Mission Peak Brass Band
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Adams E1 Custom .5mm
Hirsbrunner Exclusiv 479
Besson 2056-2, 955, 982, Imperial Euphonium & Prototype BBb helicon