Even if they last that long, the most important thing you should be storing in the long term is your backup seed. Anything can happen to your device in 50 years, but if you have them, you have your coins.
Tryninja is correct here.
Even if the manufacturer says it will last 30 years, that doesn't matter as long as you have your seed.
In 30years any device you use now will not be compatible with the new ones anymore probably even USD won't exist anymore.
What matters about ledger is that it garantee the seed was safely generated and stored. And you can make your transactions now safely