The only reason I would say to not store it for long is because you do not want to leave acidic or caustic chemicals hanging out in your vessels for a long time as they can damage the insides. Also, when you store liquids in your keg while leaving a headspace with oxygen, you create a line of difference of oxygen where the headspace has oxygen which helps with the passive protective layer of SS while at and below the liquid line now has nearly no oxygen and that can cause you problems in the long run. Just don't leave it in too long and don't make a habit of it IMO. Hope this helps.
- ISM NRP