How long can a effectively age these beers

I can only speak to the DFH beers here, but I've enjoyed the WWS and 120 most at three years and 18 months, respectively.

 

That's a lot of good stuff.

120-min: up to 5 years with confidence.
Parabola: 3-5 years (but why? It's drinking beautifully!)
DFH WWS: 5 years or more (not a big fan of this beer, and I feel it needs a least a few years)
Sucaba: 2-5 years (also already drinking beautifully)
Stickee Monkee: 2-5 years
Velvet Merkin: probably less than 2 years

 

Velvet Merlin isn't really a beer designed to be aged, it's only 5.5 abv. From Firestone Walker's webpage on the beer:
"so it is best when stored at 44F or below, out of light and within 120 days of the bottled on date"

Where as the webpages for Sucaba and Parabola say:
"Our Proprietor's Reserve Series, Barrel-aged beers are built to be aged carefully. Storing in a dark place at or below 40F will allow them to best age for several years."

 

I think he has a bottle of merKin, not merLin. I had last years merKin a month ago and it was wonderful.

 

Woot and Abyss, good beers that should hold up but I am not sure there is much to be gained. Sucuba, Parabola, Stickee Monkee are all great beers, generally the FW -bal offerings are fantastic fresh and with age, though I do not see much significant improvement.

A few questions you should ask yourself before you age anything.

-Have you drank this beer before? If no, rethink aging it.
-Why are you aging this beer?
-What do you hope to gain from aging this beer?
-What characteristics in this beer lead you to believe this beer will benefit from age?

I am under the opinion that you should not age a beer unless you can appropriately answer these questions. With that said, I do respect the educational value of experimentation and realize that one must have experiences to gain knowledge. Don't overthink everything, but do think about why you are aging the beers in question. There are a lot of rather reasonably priced beers out there that you can "practice" on, some of these heavy hitters you list I would hold off on experimenting until you feel more comfortable with your own preference regarding aged beers.