What is the point of joining an organization like Alcor and paying substantial yearly dues? Why not wait until you are in extremis and then sign up? Of course that won’t work if you die suddenly, but if you die suddenly what are the odds that Alcor will be able to freeze your brain in time anyway?
I’m not a ‘cryogenic fan’ I think, but my WAG is that many members see it as a donation to R&D, so that my the time you die, Alcor might actually know what they’re doing. 
Pretty much. Alcor needs about 1000 times the budget they currently have in order to do what they are trying to do reliably. If you actually want to maximize your chances of surviving, you better pay your dues. Not just your dues, but the extra fees for the standby team that will travel to your location when it happens.
Even then, they don’t have the kind of dough they need to have, but it’s better than nothin’.
Furthermore, if you really wanna make it, you want your last days to be spent in a hospice/nursing home that is friendly to Alcor, and you also want to be “lucky” enough to have an illness that you can somewhat control the time that you die at. Alcor’s best case that I read about was one where the man was on a ventilator, and he legally was able to ask for it to be turned off, after the team was all ready to go. His brain surface actually was clear of clotting.