My first cham was Kenya, my male Jackson's, and he has been easy in my opinion. I wasn't ready for a cham and didn't know what I was really doing. He survived for 3 months being watered less than he should have, having a compact UVB bulb, a small screen cage, and only fake plants. I also didn't gutload crickets or superworms. I found the forums and started reading away and made some huge changes and he flourished. I still have him and am expecting a clutch any time now.
I think I got lucky with him because where I live is naturally very humid. If I had lived somewhere dry, he would have had more problems.
You should get a Jackson's if that is what you really want, but have the setup up and ready and tested out, and a misting system would be a good idea so you don't have to worry about getting him the proper humidity and hydration if you will be working away from home for 4+ hours a day. You will just have to do some extra research before purchasing him (from a reputable breeder and at over 6 months if you can)
As to ask one of your specific questions, yes, some Jackson's will die for no
apparent reason before about 7 months. My theory is that since they are an oviviviparous species that they are all born, no matter what, and if they had been in eggs, some wouldn't have been strong enough to break through the shell. Instead, these weaker individuals are dropped anyway and wander off into life unprepared. Jackson's are also smaller as neonates than other species that come from eggs because there is only so much room in the mother so it makes sense they would be smaller and therefore a bit more delicate. Since they are kept inside their mother the whole gestation/incubation period, they are also fully subjected to her health. If mom isn't healthy, the babies won't be healthy because they directly depend on her, just like mammalian babies.
