What'd be better? To add one more local variable, or to call a method twice in general case?

I hvae the method which returns java.util.Date inside the hibernate-entity class: package ua.com.winforce.loto_partner.commons.db.entity;

@Entity
@Table(schema = "pr", name = "publice")
public class Pr {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;

    @Column(name = "reg_date")  
    private Date regDate;

    //GET, SET
}

And in a method I need to create the local variable which will be hold getRegDate(); value, or to invoke that method twice. What would be more appropriate in that case? I mean, in the first case we're potentially closing the moment when GC will be triggered, but in the first we waste our time to the second method invokation.