controversial opinion:
Fallout 3, NV, and 4 can only be played through once or twice enjoyably. Anymore times and you need mods/survival mode etc. to actually have fun in the 3rd play-through and onwards.
i mean
i got through 4 playthroughs of fo4 for all the endings with a collective few hundred hours invested inbetween them without any lack of enjoyment, aside from maybe the minutemen ending which was the last one i did and undoubtedly the worst. 4 by any means isnt a bad game, I quite frankly fucking adored it - but it wasnt built to be played for thousands of hours, as much as they tried.
after that i've made several attempts to play through it again - without and with mods - and i've been unable to enjoy anything past level 10
as for fallout nv i've only ever managed two or three fun playthroughs yeah, tried many times to get back into it with little success
3's kind of in the same basket