Well some have been fundraising for a very long time so I wouldn't say that's a criteria if or not one is in or out or when. Come to think of it Reagan wasn't in until Novemeber I believe..some don't enter until their war-chest is more than just a promise...a bird in hand is always a good thing.
And you forget perhaps...this election ahead is unlike any other...some will not weigh in until those clearly on stage now are spent.
So no...you just aren't right about this.
Reagan was a serious contender four years before 1980. He had been “in the arena” since his famous speech for Goldwater and his two terms as governor. For all I know, his fundraising at this point in the campaign might have been deficient, but the cost of running for president back then was no doubt less than it is now.