Now that the Volcanic Ash has seemed to be "solved" for the moment, Philip Glass' tour of the Netherlands and the UK in May hasn't been affected (knock on wood). Just looking at the philipglass.com calendar, it appears to be a particularly grueling schedule for PG and the Ensemble with get this, 11 concerts in 16 days.
Normally, I would say that wouldn't be a big deal if it were a rock band or even a touring broadway show doing the same show every night. But it's the nature of this repertoire which makes it remarkable. This includes 2 performances of Music in 12 Parts, two Koyaanisqatsis, a PGE Retrospective concert and a chamber music concert in the first week alone.
The next week the band hits its third country of the tour for two more performances of Koyaanisqatsi, but this time with orchestra in the European premiere of the orchestra version in Bergen with the Bergen Philharmonic.