Lifetime warranty depends on the vendor/provider not Hynix.
We haven't been provided any details on warranty or where this comes from, the actual manufacturer however are fine, and are not an irreputable company, and there's no reason not go for them if they're RMA'd to the company you buy them from and have a decent warranty.
The OP asked if Hynix are fine, which they are, the rest depends on the packaging company!