I hope you're also buying your borders and backing now? ... you won't find them in 20 yrs! Sometimes you can't find fabrics even 1-2 yrs later ... ask me how I know!
I order the backing and extra I need for each BOM. I know that if my retirement income becomes very limited as time goes by I have my quilt stash bought at today's prices not the price I probably couldn't afford in the future. I don't want to have to choose food or fabric. LOL.