In general, all my [historical railroad research and] reading has shown that these home-road-stations dedicated services stopped being express and exclusive within 5-10 years of introduction.
In some cases they found they could do it better with/ through other express services. Some roads changed paint jobs quickly, demoting from express to standard service OR in some cases I recall, other specialised dedicated service. From East coast to West, many of the special paint jobs were later seen in standard freights.
FWIW, davew