I think 2 inches in a year is VERY optimistic though not impossible. I too have read a couple stories like that but they are few.
10-15 minutes isn’t very long, although again I have read from a few here at Thunder’s that they don’t spend much time but do get decent gains.
If you are looking for length I might suggest you also add stretches to your routine. And it is the general consensus that beginning by warming up the tissues for 10 minutes or so is helpful because it may help the tissues to stretch easier.
If your plan is to use cold water and cool down, it may be best to do it while you are maintaining an elongated state, So the tissues “harden” longer rather than shorter.
Read as much as you can in here to get different opinions and options/ideas.
If you haven’t yet, read the FAQ’s., and newbie forums.
Don’t get discouraged but for most this is a long term project.
Oh yeah, and Welcome!