Up until a month ago my policy was strictly don't ask/don't tell. The unspoken rule in my family was no open discussions about finances. Of course this was for our generation only; our parents always shared openly so that we could assist them and we were always happy to do so.
But after I got the shock of my life during an ER visit last month, I felt an urgent need to open it up to all my beneficiaries immediately while I was still functional, so that's what I did. My situation is complicated by a highly uncertain timeline, it could be months, years, even decades, all of these currently with similar likelihoods if I read between the lines correctly. More data is in the pipeline so clarity should grow quickly.
In the meantime I'm assuming the shortest horizon and so have dumped all of my details on every one of my heirs. My family has been very supportive in my efforts to catch up on all of the forms and paperwork that could conceivably be useful depending on where I land. This includes impairment scenarios which apparently are more likely than imminent death based on what we know so far. I'm finally caught up except for my will which I've just finished drafting an hour ago.
So count me in for "notify with $ amount", but I can't say yet whether this is "well in advance".