I'm about to replace my stock Shimano BR-MT400 hydraulic disc brakes. The cables are external. I think I have a sense of how to install, bleed and bed-in the new Maguras, but is there some best practice around removing the Shimanos to keep them in working condition? In the short term, they're going into the parts bin, but they may eventually get put on another bike or donated to the co-op.
Specifically, is there any harm in letting the oil sit in the system or should this be flushed out before these brakes go unused for a while?
Any other recommendations for safe and sound removal are welcome.