Do dental mouthwashes that are 99% germ kill actually necessary to buy year after year? i know my choice to or not. i brush, floss, do quarterly perio cleanings, have my share of crowns, had osseous surgery across all bottom teeth. just wondering?

With your oral hygiene practice it is unlikely that the mouth washes are adding anything to your oral or general health. Wish you good health!

Probably not necessary. Flossing/brushing disrupt dental plaque preventing harmful byproducts. Periodic Perio cleanings reach the areas that you can't reach. Sounds like you are on the right track. Mouthwash is an adjunct to your regimen, providing possibly an additional 1% of efficacy. Talk it over with your Dentist. (S)he seems to have you an effective Oral Hygiene program.