You always have to keep the probe wet or it is destroyed. New probes are expensive. ~$40
I used to keep a small cup with lid, and cut an X in the top of the lid. Added ro, and pushed the probe through it to keep it wet for storage. This past week, I put the probe in my crs tank as storage, and to monitor readings continually.
http://aquariumsupplies.marinedepot.com/search?w=pinpoint&modaf=null
Check the above link. They have some great specialty meters I'd love to have one day. TDS, Nitrate, even O2 readings!