I've sewn my own face coverings (I used to make quilts and have a large amount of fine-woven quilting cotton to use!) and have, um, four I think. Plus a Buff. DH has three and DS1 has two. (They don't go to shops really.)
Following the instructions from a renowned virologist whom I trust, I wash mine in hand-hot soapy water, as it's really the soap that kills this virus - the fats in soap break down the fatty capsule of the coronavirus. I then line-dry.
I've got a sort of line in the sand regarding how often I wash. If I wear it for five minutes, say, to pop into a shop and there are hardly any other people there, I'll wear it again. I'm fairly comfortable just popping it back into my bag. But if I do a supermarket shop where there are loads of other people, I take it off carefully, bag it and wash my hands, then it gets washed as soon as I'm home (ahem, mostly. Sometimes it sits on the floor of the car until I remember to). I'm sure someone will be along shortly to tell me I'm Doing It All Wrong, but I think it's fairly sensible.
Don't bother washing at 60, people! Just use lots of SOAP.