How long did it take to make fallout 3?

I made it less than 1 week only . (with no DLC)

if you play it 3 hours a day , you'll finish more than 2 mission indeed.

(that's if you uncover all the location in the wasteland)

With the EXPLOLER Perk , it'll be Easy for you to found all hard Locations there, sometimes you'll very need this perk , 'cause one or two quests here need to be uncover and if you don't have this perk you'll be exausted (like i did) . Example : "Agatha's Song" you must know Vault 92 , if you don't have this Perk , you'll take a long long way to the capital through the Subs , Raiders , Ghouls , Roaches , sometimes Muties and then you find the info 'bout where's the vault is . So ? take the Perk right now :)