Tend to be used much more intensively without much of a midday lull (in Network South East days regularly about half fleet was parked up between peaks and from mid evening)
Many now seem to be diagrammed nearer 16 hours a day.
That’s an urban myth. They were used quite intensively when they were at Reading.
Taking the 1996 diagrams as an example (and excluding any intermediate shed time), the 2 cars were out for a diagram average of 17 hours 57 minutes, the 3 car 165/1 for 14 hours 55 minutes and the 166 for 16 hours 56 minutes. Daily average SX diagram mileages were 394.4, 397.8 and 595.7 respectively.
The Donkey unit was the one that out the longest. It left Reading Depot at 0127 and did an overnight run to Pad and back before going to Maidenhead and then onto the branch, where it worked all day. It arrived back at Reading Upper Triangle at 0103 the following morning.
Only 1 x 2 car and 4 x 3 cars stabled for the entire inter-peak, all at OOC - 5 units out of 51 diagrams. There were a few others that came on OOC and RDG for a couple of hours only, mainly for a sweep out at the former and fuel at the latter.
I do remember that the number of units stabling during the day dropped further in the following year as the fleet was used even more intensively. Reading could deal with this intensive use as it was set up to cope.