That is really cool that your company will make a payment to your HSA insurance account like that! I have never had an employer do that, although it would lead me to appreciate management a lot more. Does the unused total roll over at the end of the year for you, too?
Yes, you don't ever lose the amounts left in your HSA. Even if I left the company I could still role over the funds I have to an HSA at a new company or could role it into my 401K. This was our first year with an HSA and I was nervous, but I am really enjoying it, and also love the feeling of security I get from having almost $3500 set aside just for medical emergencies or care.