I didn't see much on dealing with going to races at altitude in this forum. I'm guessing this would be more important for shorter races, but for Ultras what is the suggested time period for acclimating?
The old advice is as either long as possible before or immediately before the race. Dunno if there's any science behind either though. I honestly can't tell any difference between a day, two days, or two weeks... though I live at a moderate elevation (5500').
You'll ruin your knees!
Different things work for different people... at different times.
I have a buddy that has 7 Hardrock finishes and 2 near finishes... last year, he was up in Silverton almost three weeks before the race and had to come back to TX due to HAPE several days before the start of the race... never had problems before that.
I have another that went up the night before and got pulled at 30 miles into the race due to altitude-related blindness... he learned that had he continued, he could very well have done some major damage to his eye(s).
I have heard many suggest if you can't do two weeks, don't bother to go early... I went up 1 week before and had no issues the two years I have been up there.
Bottom line... YMMV
Good luck!
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""...the truth that someday, you will go for your last run. But not today—today you got to run." - Matt Crownover (after Western States)