I agree with kcokayne.
Many years ago, during night duties, we band-boxed Air and GMC onto 1 frequency at night, which involved cross-coupling 2 VHF and 2 UHF channels.
As nights became a bit busier, the airlines complained about having to listen to GMC stuff when they were on the ILS, resulting in both frequencies being kept open, but manned by 1 ATCO.
No-one, including the younger folks, enjoyed doing this. Two frequencies was often hard enough.......Let alone two airports.
Just out of interest, are there any area folks who operate 2 widely-spaced sectors simultaneously on different frequencies? I know EGGP do EGCN approach from Merseyside, but I don't know if they are licenced to do both at the same time?