Is my data safe in imdb. If I won't rate any movie for year then data going to remain safe?

Yes, your IMDb data will be safe if there is inactivity in your account. The only thing that would impact the account data is if you decide to delete your IMDb account, so as long as the account remains active, even if there is inactivity, none of the account activity will be affected, so all your selected preferences, reviews, votes, lists, etc will still remain active.