It’s impossible to say exactly how long it will take for you to master a particular skill. What defines a “triple-A quality” asset? How much time can you dedicate to learning? How naturally does this particular skill come to you?
As Jezcentral says, put together a portfolio. Come up with a project you want to work on, perhaps a character you like from a game, film or book. Create the model and produce some nice renders for your portfolio. Now maybe you want to put them in a scene, so start creating the scene, again using something that has inspired you from other media. Now maybe you want to try animating the character in the scene, so start working on the rigging and animation. Finally, you could decide to add some special effects like fire or smoke to the scene as well, so start looking into the Cascade UI. Keep building up the project, add something new with each iteration to develop your skills further.
The length of time it takes to develop the skills necessary to create work that would get you noticed at a major studio is the length of time it takes for you to create a scene that looks like it would meet the standards of a major studio. Quite simple really. Go for it!