Im not saying never have a military, But tell me what threat should they be worried about requiring the build up of thier military now ?

If the situation changes in 50 years time sure. As things stand they have saved themsleves 50 years of unnessecary expense, and i see them saving themselves another 50 years of unnesecary expense... all to the benefit of Costa Ricans and the dismay of wargamers and military enthusiasts !