Good for you on your past success. I can't imagine why you couldn't reuse the vermiculite or bags unless you have a couple soupy rotters or obviously diseased tubers in a bag. Then I would get rid the storage medium inside, maybe the bag too.

I'm curious how much sulphur you put in each bag. That sounds like a great idea: two birds with one stone- antifungal right in the storage vermiculite.

Yes you can save it from year to year- there's no way we could afford not to. Just make sure you store it over the summer in tightly sealed plastic bags & where it won't get wet- it'll seep up any water it comes into contact with if in a gunney sack or loosely woven bag-- & as Poochella said, toss any that has had a rotted tuber in it.

Thanks, Poochella and Plantlady, it helps to know i will be able to save some money.. All the Dahlia i grow are for the gardens at a care home for the elderly where i work.. I worked in mining most of my life and took up gardening 2 years ago, and enjoying every minute of it, but have a lot to learn :)
I put about a table spoon of sulphur or a little less in the bags with about 4 or 5 handfulls of vermiculite depending on how many tubers went in and gave it a good shake.