That kind of hardware wallets start to gain more and more ground lately. Even the old "established" Trezor is open source (just it doesn't have Secure Elements chip yet). A list is here: https://bitcointalksearch.org/topic/secure-element-in-hardware-wallets-5304483
And if a HW is open source for, let's say at least 6 months, I am 99.999% sure that multiple tech savvy people have checked it over a couple of times.
I don't realistically have such hopes. Sooner or later it will break, but I guess that it won't happen for at least 5 more years. My hope is that the technology will be better and cheaper until my HW dies off.
Luckily Nano S doesn't have its own battery. I just don't like this new mess up (c) by Ledger.