From Lee Millard on the Facebook group MND Warriors....

The 2 or 3 months is highly misleading as it is based on the 3 original trials which only lasted 18 months. So the conclusions could only be made on that period. What about someone who has taken it for 5 years or 10 years?

Now 20 years after the drug arrived, data has been reanalysed, along with real life experiences, and the general view is that it gives 10% extra life. So someone on it for 10 years, might get 3 years extra.

This is not as crazy as it sounds, as for a cure we need a many 100% improvement/extension but also someone who experiences fast progression, the extension will be short, like 1 to 3 months.

Here’s a recent paper