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Personally, I've never tried to do "100% completion" with any character in a Beth game. I find it more interesting to play until a specific character is boring, or "done", then try again with a new approach. And by leaving some things undiscovered, that means I can find *new* stuff with my later characters.
Not to say that I don't wander, or that I just do the MQ and then stop....... example: My first FO3 character. I finished the Main Quest at around ~25 hours (did a bunch of the sidequests first, too - I was level capped before I followed the MQ to Galaxy News Radio). And then I continued playing with that character for another 50 hours.
At that point, I decided to try a different character.
I don't think any of my dozen+ OB or FO3 characters have ever approached 100 hours played. But there's always another character to play, and more new things to find over the next hillside - that's what's so great about Beth games! Always more to see and discover!