I purchased most, if not all of my PP, site unseen. Of course the requisite research was done, but in truth my "diligence" isn't particularly useful. With or without, I don't think I'd have ever made a different decision on a piece. I'm not sure others would agree entirely, but in my experience I know - with almost 100% certainty - whether a watch is for me based on i) simple marketing photos and story / significance (e.g., 5650) and / or ii) experience with other, similar, references (e.g., Nautilus family).
Or, perhaps I've simply been lucky to date...long may it continue 😉