For me it's one year to keep Windows Mixed Reality working. I'm still miffed that they pulled the plug with no alternative other than putting my headset in the bin and get a new one...
If you haven't looked into it Monando might be what you need to keep your headset running. May not work for your headset (doesn't for mine but mines not WMR and is because of my 8kx's driver)
I already did back when Microsoft announced they would drop WMR, but it was (and still is) pretty experimental, with no controller support and 6DoF requiring external tracking.