The "standard" recommendation seems to be hysto within five years. In fact, I was hassled about it the penultimate time I went to the clinic last December. "Our records show that you have been on T for four years and ten months. You need to have hysto! Now! Right this freaking minute!" I said I was planning on it at the end of 2014 (I was, but that fell through), and I was told that I was pushing it and had to have hysto within five years.
Okay, I exaggerate about their reaction, but only slightly. I was treated with disapproval at an almost-free clinic for indigent people because I was almost five years on T and hadn't had hysto yet. I had uncertain employment, and, unlike MANY of the trans men there, I had just acquired health insurance not long before. And for all the clinic knew, it didn't cover such things. Don't be so damned dogmatic.
I have never heard of the two-year recommendation, and even the five-year recommendation was not based on ANY kind of empirical evidence the last time I checked. But then, I'm not a doctor or a medical researcher, so maybe I'm underreacting.