Contact Adobe customer service. They will usually give you a free upgrade if you've bought the old version within 30 days of the new release.
I don't know about 6 months though. However, they do offer a special "upgrade" price, if you ask for it.
That said, though, I'd look over the new features article in the link below and see if there is anything compelling in it.
Many people are facing a lot of challenges with version 8 and are actually asking for a retro-gade back to version 7! So, unless there are features you are specifically interested in -- and you have a relatively new, very powerful computer -- you may want to hold onto what you've got.