Yeah it was a bit messy in the old days - you would have at least 6 weeks of Scott and chris covering for Moyles/Grimmy in the year, as well as odd days, so many times specially during the Grimmy era they were called last minute to swap into Breakfast
Then theywould both have about 6-7 weeks of a year as well, and many times not together so if Chris was off Scott would do the show solo and if Scott was off Chris would work with Matt, Alice, Jordan etc
Many times Scott would start his own leave after two weeks on Breakfast as well so you would get 4-5 weeks of no Scott on drive or lunchtime
I worked out just on the standard leave quota Scott was not on his own slot for three months a year plus any ad hoc days Grimmy used to call in sick, take a short notice day off etc (the one i remember vividly was the one where Grim was injured in the football match on the Sunday)