My cat is “newly” diagnosed. Vial says good for 42 days. It’s about that time and I still have 1/2 of a vial left. He’s on 2 units twice a day. Has anyone tried the pens? Would they be more economical at this dose? With insulin so expensive it would be nice if they sold it in 5ml vs 10 if it expires so quickly. :(. Any advice is appreciated!