Just to try to get some data to this discussion (rather than solely relying on anecdotal evidence), this is the most recent cycling sheet I've seen
posted and I highlighted with yellow rectangles all overnight visits at MMC:
View attachment 625751
As you can see, Venture and LRC sets get regularly (i.e., at least once every 7 nights) to MMC, whereas I only found
four five gaps of more than 6 nights without visiting MMC:
- Venture Sets 1/2: 9 nights without MMC visit (from Thu Week 1[V1] to Sun Week 2 [V2])
- Venture Sets 10/5/6: 8 nights without MMC visit (from Sun Week 1[V10] to Tue Week 3 [V6])
- Venture Sets 7/8/9: 9 nights without MMC visit (from Mon Week 1[V7] to Thu Week 3[V9])
- Venture Sets 12/4: 7 nights without MMC visit (from Wed Week 1[V12] to Thu Week 2[V4])
- LRC Sets 10/11: 9 nights without MMC visit (from Tue Week 1[L10] to Fri Week 2[L11])
Therefore, I'm slightly doubtful that Venture or LRC trains operate weeks without cleaning, though I have no idea how the HEP-II consists are ever getting cleaned, but maybe they have some hand-operated equipment...