I am almost 9 months post, 4b and I get my hair professionaly blow dried and flat ironed weekly. I've been doing this my entire transition. So maybe my hair is "heat trained" now, but I rarely have a problem with reversion unless I break a super serious sweat. The roots and edges may puff up a little, but it stays relatively straight.
Even if I do a super intense cardio exercise session my crown will have no visible reversion. You can touch it and feel little crinkles but just looking at it, its still straight. The back reverts quicker; i just sweat more in the back of my head, i guess and maybe the texture is different.
Since I work out during the week, I only wear my hair styled and out on the weekend. Then during the week when I work out, its pulled back in a phony pony. But if I didn't work out, I could go about my daily activies without any major reversion.
http://www.longhaircareforum.com/showthread.php?t=325829
I think Ive always had the misconception that my hair type was harder to straighten and stay straight, but I don't think thats the case. Its like bc I don't really have a curl pattern, it may be easier to straighten. I had a co worker who has beautiful 3c hair, and she walked into a gathering with a silky bouncy fresh press. Then the activies moved outdoors where it was dreary, humid, and misting. Her hair swelled up and reverted in a matter of minutes, it was puffy and frizzy and had lost its shine. she ended up pulling it back in a rubberband, you couldnt even tell she'd gotten it done. My hair stays straight, even in humidity, its not going to revert unless its almost soaking wet.