I did a specific training that took me a few months (3 to 5, difficult to remember, I had bought the program online, we are talking 2002), with plenty of negatives included that worked very well. I also had to file down a gripper to make the range of motion larger--the negative rep (which means closing with two hands, and open the hand, that is doing the eccentric part of the movement, slowly) in the "filed down" region was particularly effective.
If you could do 4 reps with a #2 with no specific training, I am confident that with targeted training and progression within a year you will be able to close #3. Worthwhile? I don't know. But closing #3 was as satisfying as getting my black belt in jiu-jitsu.
I'd take the black belt a million times over. That's a rare and magnificent treasure, where skill easily trumps strength. It is also extremely difficult to acquire.
It's really hard to get a black belt, it took me 10 years of consistent training in the art and a year after getting it I still don't feel like I'm good enough. That's okay, because it keeps me on my toes: when I feel like I don't want to train, whether it's jiu-jitsu, boxing, cardio or weightlifting, I'm reminded that I have a black belt and I need to "honor" it.
But feelings are feelings, I got a PhD in three years, close a #3 CoC in 6-9 months after getting them, and I got a black belt in 10 years. In terms of "joy of accomplishment," I would put 1) black belt, 2) CoC #3, 3) PhD.
