Though you might not be able to get a "perfect" time that you want, I'd assume that you should be able to get the tier 1 you'd like. You might have to keep trying, don't assume that if what you want is not available on t minus 30, that something won't become available on subsequent days. I'd grab the best ones available, and then keep looking/modifying - probably often. Ppl change their plans all of the time, and change their fastpasses.