Should I redirect deleted category – How long?

If I delete a category for good (didn’t have but five posts in it and I moved them all), should I use a redirect to point to the new category? If so, how long should I use the redirect?

Otherwise, would it be best just to not do anything and let the Google just drop it out its index in a few days?

Thanks for the help. I’ve searched this a bunch, but there are never really clear answers on what’s best it seems. So many opinions that I wanted to ask myself.