It took my dad last year, diagnosis in April, gone by mid-June. It was so aggressive he chose "medical assistance in death" (MAID), because he didn't want to be in hospitals all-the-time. He had half-completed the process, then had a stroke on June 4th, where he was then admitted to hospital. The stroke cause aphasia, so he couldn't communicate very well (speech was very disjointed, but he could understand everyone) - they brough in a speech pathologist, after a couple weeks they we able to confirm that he still wanted 'MAID', so - I had to make the decision as to when. (And - I agreed, spending time in hospitals, fighting the inevitable was antithetic to his whole personality)
Cleared by 2nd round of medical professionals to make the MAID decision on a Wednesday, so - we scheduled for Friday - he passed away naturally Thursday morning.