Buying 1.41Tb for $36 isn't the entire story. After that 1.41TB is exhausted, you have to buy another 1.41TB. And then another. So, just assume you will spend $72.
I just bought a 1TB pocket hard drive for $55, and I can use that over and over and over. And the best thing? I can make incremental backups.
I guess you could do that using DVD-RW, but that's not what you bought AND it'd take forever and a day.
Locally, I don't do incremental or differential backups. Too much of a pain when restoring. Also, I keep backups for a very, very, very long time.
That being said, as noted earlier, I also back up onto hard drives. However, the biggest problem with hard drives, is that one good failure will totally wipe you out. DVDs, on the other hand, are much more resilient (no moving parts!), and each one functions independently, so if one goes, the rest are still good.