I'm not sure that the gridview is the problem here unless you manage to stuck a years worth of data in one page.
If you have a gridview with 100000 records and you show 10 on the page the viewstate will have only this 10 records info, maybe you are doing something wrong?
If you only display few records at a time and you still get humongous viewstate then can you provide a snapshot of the viewstate you get and the gridview records you have?