UK TV silly season – beginning date and trends?

The quality of evening TV broadcasts on Freeview (digital terrestrial)
seems to have taken a real dive of late. Is there a TV silly season,
analogous to the news media's silly season? If so, around what date
does it begin? And is there a recent trend towards the TV silly season
beginning early or later each year?

Are there any places on teh interwebs where such issues are discussed?