You're right. we keep talking about long term investment of 4 to 8 years which is estimated to hold for 2 times bitcoin market circles but that's by the way to such aspirations. There're certainly investors who has been determined to hodl their bitcoin while a working class untill their retirements before they can begin to sell or take profits out of it and this could be a matter of youth age to an old age within a distance range of 15 years before they'd hit on their wallets.
Such investors are not panicked about what the market brings in a main time because they knows that as much they holds, they'll definitely make it bigly.
I think who're skeptic about such investors would muchly assume their wallets are lost, abandoned or dormant.
I don't think of any possibilities of any investors engaging to invest on bitcoin over a decade because it can't be imagined of what generation you'd be investing for when you, your children and the grandchildren ain't going to benefit from it.
So dormant wallet can only be determined by time factors that it has been on generation to generations without being active.