It may be a matter of degree. My experience is that warm intros do help for early stage investors, but they aren't a requirement. Maybe a simpler way to look at it is that a warm intro often helps any introduction no matter who it is, but if you're polite, direct, and charming, you'll be fine either way. Since it was qualified as "a lot of time", I'd suggest spending "a little time" trying to get a warm intro, if that doesn't work quickly, just email cold while keeping the posted advice in mind.
