Throughout the class 27 era there were actually five sets in traffic each day which meant each set in turn came out of service for an hour or two through the day for servicing. The fifth set was required for one morning peak additional from Edinburgh to Glasgow and evening return and enabled the sets to rotate in this way. When the 47/7s came on the scene this arrangement did not continue for very long and the peak extras were then covered by sets which did other, non E&G, work during the day. Come the class 170s again these were rotated in and out of the E&G workings so in all cases, whilst still fairly intensive, not quite as intensive as it might appear at first glance.
In per covid days TPE had a class 397 diagrammed to make five single trips between Edinburgh and Manchester Airport - 06xx 14 xx and 22xx from Edinburgh and 10xx & 18.xx from MIA - including ecs miles Polmadie to Edinburgh and Airport to Longsight this was over 1200 miles, quite impressive for any service not benefitting spending the day on the faster routes to/from London, and with turnrounds of around 20 mins at the south end and around30 mins in Edinburgh not much margin for error. The 'day' from leaving Polmadie to arriving Longsight was just over 22 hours, and the total mileage for the day roughly equivalent to three single legs between London and Edinburgh or Glasgow.