Spindle Cooling System when not in use

Good Day all

I have a 2.2KW Water cooled spindle on a 6040Z CNC router. My cooling system consists of a 10 litre reservoir that sits on a tier below the router bed with a pump attached to the reservoir. I've also mixed a glycol based antifreeze for contaminant protection purposes :P
I've noticed people here use a wide variety of solutions from the really cheap DIY to the hardcore fancy stuff, however I was wondering what everyone does with their cooling systems when not in use.

Do you drain the pipes after you're done? Drain them every few weeks or so? Make sure the liquids regularly flowing?
Or just leave the liquid in the pipes?

Not sure if these are obvious questions that my mediocre googling skills just haven't been able to answer but I'd like to know what people are doing in this regard :)