I heard that the higher the data density on DVD and BR means the higher the failure rate. Though i have no real evidence of that myself.

Maybe one or two bits corrupted here or there will only cause some unnoticeable artefacts anyway.

Music CDs or data? Music CDs have built-in error correction, data CDs don't. You can certainly extend the lifetime if they're stored in the dark in a cool, dry place (UV light, heat, and humidity all damage the dye that gets burned to encode them) but they're not reliable archival storage without error correction.