Anything small enough goes in the machine - thermatex, coolers, fleeces etc get washed after every use - I have a grey!!!
Stable rugs - I tend to keep something thin and easily washable as the base layer, then the top one the same for as much as possible then if that doesn't fit in the machine it will go to be cleaned.
This winter two will go for cleaning and one for repair, but I've used 12 different rugs between two horses.
I wash all my stable rugs, fleeces, coolers etc at home and send all turnout rugs away.
Just brought seperate washing machine and tumble drier for this purpose as OH kept complaining.