DVD burners have reached a level of standardization where they're pretty much considered an "accessory" a little like "third party auto parts" that are interchangeable (i.e. meet a manufacturers specs). This is not to say that there aren't differences, but most people don't pay much attention to which brand name is on the box. It will be of interest if you can identify differences that actually affect performance.

There is the distinct possibility that a particular brand will come with bundled software/drivers that will make a difference that's more important than who made the hardware. I'd suggest paying some attention to that possibility, although most makers/sellers don't really reveal much.

After a year or two of use, it is possible that you're running into mechanical problems with the burner, but it's also plausible that simple crud and corruption (dirt etc) has accumulated that could be remedied by some maintenance of the device you have.

Also to be considered is whether you may have accumulated some software/driver corruption, that could be eliminated by removing and reinstalling the programs(s) you use (especially the driver for the burner), and/or by checking with the maker(s) for driver updates and/or drive BIOS patches.

Assuming that you're burning from a "clean machine" that's up to date with defrags, drive space, no unnecessary startup crap in RAM, and all the other goodies, a disagreement between the physical result on the DVD and the reported result does suggest that the problem may be somewhere in software rather than in the drive mechanics (but not conclusively), and of course a new drive and the software interface that comes with it may be a lot quicker than worrying about what's degraded in an existing setup.

As a curiosity only, WITHOUT RECOMENDATION, a recent (snail mail) advertisement suggests one can get about as fancy as you want. The ad was approximately as shown at Primera. I know nothing about these people or their stuff, but it might be of sufficient interest to someone to be worth checking out (for something to talk about at the pub?)

John