If the idea is to store the SSDs for 50+ years in a box with the hope of recovering the data from them, I'd be more worried about compatibility and interfacing with future computers than data loss and readability. To put things into perspective, good luck trying to read punch cards these days. Even when 50+ year data recovery from a dead system can be done, it can be a huge undertaking
. As Wayne pointed out, SCSI HDDs are already getting iffy, and they were common just 20 years ago.
Recovering data from dead HDDs is possible, but I'd urge you to check just how much it costs before putting any faith in that - it costs a fortune.
Fortunately current standards, are, well, standard, and wide-spread. But many of them are proprietary which means that the specifications needed to reverse engineer them could be locked up in a company vault somewhere, or lost altogether due to bankruptcies.
Proper rolling forward of all data mediums is necessary for peace of mind, ie. floppies to CD-ROMs to tapes to HDDs to SSDs to holographic memory etc.
For the store and forget, solution for the paranoid is to store the SSDs with a complete computer in a climate-controlled environment, but that introduces many more points of potential fault and costs a lot.