I don't know that you'd "die" directly from that. If you go for long periods with neither T nor E, you will have unpleasantness emotionally and such. The biggest thing I was told about before my hysterectomy was bone density. Your bones will definitely suffer and become brittle if you have no secondary sex hormones to help support your system.
However, there are FAAB people who are not trans who have hysterectomies with ovaries removed and forego HRT. So I don't think it's a "if you go without any secondary sex hormones for 1 year, you will die" kind to thing. It's more of a "your body generally needs those hormones for proper function and you may or may not be negatively impacted to a large degree" type of thing.
As with all things hormones, it affects different people differently.