Traditional Free Grace theology tends to be a bit vague about the eschatological consequences for unfaithful believers. In contrast, Zane Hodges, Bob Wilkin and Joseph Dillow make a powerful case that unfaithful believers will suffer loss of privilege and co-heirship with Christ.
While I think that Hodges/ Wilkin/ Dillow make a compelling case, a weakness of their position is the assumption that non-overcomers will be either in heaven or on the earth during the Millennium. The older Millennial Exclusion view holds that non-overcomers will be excluded from the Millennium and will be incarcerated in hell (Gehenna) during that period.
The idea of born-again, justified believers spending time in hell seems shocking, but there are some good reasons why this might be the case.
1. They have enjoyed the pleasures of this world. In hell they will see the consequences of the world's activity.
2. They have received the benefits of Christ's death yet have neglected to live out the implications of the cross in their lives. Experiencing hell temporarily will teach them the reality of what Christ saved them from.
3. The unfaithful lives of these saints prevented them from being a witness to their neighbours. In hell they would see those that they neglected to witness to.
This is not a nice idea, but I do think we should consider it.