A mobile depot by its by nature and (one of the) intended purpose(s)/use case(s) should be semi-permanent. It needs to be something that sticks around for you to come back to in a region of space you are operating in. If it enters abandoned state, then you lose your stuff in one attack, and if you lose your stuff so easily, nobody will want to use it, and it nobody wants to use it, then there’s no point to having it exist.
Unless you have issues with mobile depot spam at tradehubs, having mobile depots take 30 days to decay hurts no one while maintaining their intended functionality and keeping them safe enough for players to want to relay on them.