Here is my two cents: (keep in mind that my experience may not be relevant to you)
You never know how ALS will develop. It is better to be early than too late.
My dad was slowly losing his ability to move his legs, back, arms, neck etc. In the morning of being sent to ER, he had a good meal; no one foresaw what happened next. He was put facing down for a routine scan, and suddenly he could hardly breath nor cough out mucus that stuck in his lungs and throat in that afternoon. He was soon sent to a local ER and doctors there saved his life. Two days later before my family had a clear understanding of his medical situation, we were put the position to decided whether put him on vent or not. To save his life, we said yes. My dad was tortured by the discomfort and had a minor infection in his lung about a week later. My family again, was put under pressure to decide whether a tracheotomy would be performed or not. My dad eventually choose to have one; however, he seems to be in agony every day.
My point is that when you have time and energy to ask questions, to find out answers and to think, you better plan out your death. When you take out by surprise, you and your family may be rushed into making decisions that you may regret.