A dry suit may actually be in my future. The two key factors are how cold it is once out of the water when changing into dry clothes after the dive. Everyone has a different cold tolerance. To this point in my Puget sound diving the 7mm full jumpsuit and the step in hooded vest has been fine under water for a couple hours, or two back to back tanks. I've sat out an hour between dives and at about that point it's a little chilly, I'm anxious to get back in and warm up.
I do believe if I wanted or had to dive a third dive, It would get too cold by the end of that third hour. RIght now I'm solid warm and having a great time for two back to back dives with that 7mm full, plus 7mm step in wetsuit/vest and hood.
The greatest struggle with this much neoprene is boyancy control. I need a fair bit of weight to sink, then I must tinker with the BCD inflation for bouynacy, it's a little challenging to get just right. This is only a that depth. With air in the BCD and moving shallower, volume increases and the feeling of lift is strong, back to tinkiering with the dump valve and the refill.
So at this point the cold is less of an issue for me then the bouyancy. I need to remain properly situated for nice photo's without bumping bottom and stirring up silt. JT suggested I would need a couple dozen dives with this much neoprene to really get a feel for the quick adjutments needed. Then he added "when you change a single thing as part of your dive gear, you start over! "