cat eye infection

My cat has another eye infection which I'm pretty sure is herpes and will be a lifelong issue. I have an expired tube of terramycin. It expired on 2/15/13. I did get a new tube from the vet but can I still use the expired tube. I know most medicines are still good after the expiration date but they may not be as potent. I'm asking because I have 3 more cats that will probably get it too and I would like to use the expired tube if it's safe to do so. My new tube expires next month also! I honestly don't want to take a change with her eyes if it could hurt her eyes. Does anyone know how good this terramycin is after the expiration date? I thank you for any information .

I have no idea, but I'd probably use it because I'm cheap.  LOL

I have used it after the expiration date before and it helped.