Whenever it needs it. Mike does his own and usually takes care of the towels; I do Mom's and my laundry, the bed linens and any miscellaneous household stuff like throw blankets, pillows.
With four grandsons living with me that makes six in the house I do laundry every day. I did not do much these past few days due to the death in the family no my will it take me forever to catch up
When it needs it, which is nearly every day. My husband runs and works out a lot, so it is mostly his and he pretty much does his own (NOW, after almost 30 years of marriage!).