Depends on your tolerance for filth (not a value judgement). You don't know how messy your enviroment is untih you see a robovac fill cannisters of shit each week. Having baseline for cleaniness helps with allergies. Like everything you can optmize for some big QoL gains, i.e. i basically just whip crumbs from surfaces straight to the floor knowing it'll get picked up. The solution for 2 level homes is 2 robovacs, cheap second hand, going to get disgusting anyways, replace filters and bristles. A few 100 dollars to have 80% clean floors is pretty life changing. Does not replace need for manual vaccing nooks and corners every once in a while.