There's not much hassle.
You fit them yourself.
Once balanced they'll be good for a good while until you start to lose a fair bit of tread. (just like any other tyre/wheel)
As for losing 'useful life' , they're just being used ~50% of the time (depending on your weather) , so the useful life is being split between the two sets. (50% wear on each set per year equates to 100% wear on one set per year - ish)
You could get all seasons , but they're not as good as full winter ….. There's compromises to be had because the weather is fickle and not on/off for each season, so there's inevitable wear on the snow set in the transition either end of the season, and the poor performance of the summer set as you transition into the winter season.
But as said depends on your weather, whether they're worth it ...