Good backup software is going to have methods to verify that backed-up data is intact. When backups are stored in (potentially fixed-sized) blobs, you have the option of verifying a single file in one action instead of potentially thousands.
By "dead" I'm also assuming you mean bit rot. While that's a real problem, it's not something that happens day after day at any scale an individual would be using. If the source is getting corrupted somehow and that corrupted file is being backed-up, this is what version history is for.
Good backup software is going to have methods to verify that backed-up data is intact. When backups are stored in (potentially fixed-sized) blobs, you have the option of verifying a single file in one action instead of potentially thousands.
By "dead" I'm also assuming you mean bit rot. While that's a real problem, it's not something that happens day after day at any scale an individual would be using. If the source is getting corrupted somehow and that corrupted file is being backed-up, this is what version history is for.