WE Mezza Luna Red was my first kit wine. I sampled it a couple weeks ago at 12 months and it has finally turned a corner. I tweaked a bit and fermented it on 16oz of Zante currants, then bottled 3 gallons, and racked the other 3 gallons to a carboy on some Tannin FT Rouge. The tannin batch was always a bit better, but neither were very good until recently. I still don't consider this batch ready, though one of my younger reds is about ready. Several people, however, consider this an early drinker. I'm not one of them.
I personally won't do this kit again, though I'll eventually try several of the CC Sterling line reds which are pretty comparably priced and are 12L with skins. I've never used glycerin, so I can't speak to that. Personally, I'd split the batch and try it on part of the batch and have a control, then sample them both side-by-side over the next couple years to find out if glycerin is something I'd add to my repertoire. I would encourage you to experiment with different tannins on your reds, as I (along with many others) have found them to both help reds come around a bit sooner as well as help the mouthfeel and finish. And, of course, time works wonders, so save a case (or at least a couple bottles) until the 2 year mark or later to realize its full potential.