For one thing it is just to risky
I use a syringe up to 10 times or so if I am doing a large set of vaccines and I don't get flash in the syringe. ie. blood in the hub of where the needle connects to the syringe, only use needle once, period, if I get a flash, then I toss it and get a new one, you only get a flash with IM injections not SQ, you can run a whole batch through with one syringe if you have no trouble with the plunger
And Jeffers of Valley Vet is the cheapest source to purchase this stuff, you can do it online and make a shoping list, so each time it is quick and less time consuming