Two hours is nice for exactly the reason your T says, it gives you lots of time to go a bit slower or discuss things in more detail. It probably can be hard if you are fighting yourself that whole time to tell/not tell or if you normally have trouble talking to your T for an hour, but if you talk okay in the hour, having two can help with easing some of the time intensity.

If I were you, I would write out a "clinical" report of what happened. I'd keep it sort of vague, "My neighbor when I was six touched me sexually on three occasions" that sort of thing and only start work on parts of it -- you and your family's relationship with the neighbor and how you came in contact with them, how you felt afterwards/up until now, why you haven't told anyone before (how you think telling will make you feel), etc. rather than focusing right away on the actual abuse act. Just keep spiraling closer and closer as you feel more comfortable. It doesn't have to be talked about all in one two-hour session either, it might take months (or years; my last therapy was 2 hours a week for 9 years).