First 2.4 mile swim

I started swimming 4 1/2 months ago while recovering from a left shin splint injury, and have thoroughly enjoyed it. I remember getting into the pool that first time, swimming 800m (very slowly I might add) and thinking it would take me forever to build up to the full Ironman swim distance of 2.4 miles. So day before yesterday, I went to the pool after having completed 2.0 miles a number of times, and 1:19:21 later, I finished my first 2.4 miler without stopping and without doing flipturns to simulate as much as possible an open water swim. I'm still nowhere near strong enough to do the entire thing freestyle (I did this swim alternating breaststroke and freestyle laps), but from what I can tell from other men my age (late 40's) that have done Ironman competitions, I'm not too far off the mark of the average swimmer. My goal now will be to continue to improve on my form and mix up my swim workouts with more interval type work. I do not have a specific time that I'm trying to get down to, mainly because this is all still very new to me, but my guess is that I have a chance to get down into the 1:10:00-1:15:00 range at some point in the next year. Any input on this from the real swimmers is greatly appreciated.