is there an account expiration?

Hi guys its me again i seldom play GW because im busy in school. So how many months or years if we donw evet open our account before it expire thanks a lot

Never. Once you make an account, it's permanent.

thanks a lot

Your account will never expire. This is partially because of ANet's pay-once policy (i.e., no subscription fee), and partially because deleting an account probably involves major server changes. Anet will never delete your account.
I left my storage account for nearly a year, and when I came back my account was just the same as before. Monk had developed some sort of green moldy fuzz, but nothing else had passed its expiration date.