How far in advance to mail invitations to a party depends on what kind of party or event is planned. Mailing ranges can be from as little as two weeks to as long as eight weeks.
For children's birthday parties and casual parties with no particular purpose, the generally accepted time to send invitations is two to four weeks in advance. For formal parties such as weddings, graduations and milestone birthdays, invitations should be sent four to six weeks in advance, or up to eight weeks in advance for people with long distances to travel. If the host gives notification further than eight weeks in advance, she should send a "save the date" notice, with an invitation to follow.