How often should I follow up with connections I have made on LinkedIn about job openings?

I have connected through LinkedIn and asked if they are hiring, they have all responded "not at this moment". I want to follow up but dont want follow up too soon and then alienate them.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia��).