I believe justification/redemption is irreversible. In the 'P' of T.U.L.I.P., ("Perseverance of the Saints") it states that if a believer turns away from the faith, sooner or later they will return; and if an apostate does not return, they were never redeemed to begin with. Generally, I agree with this point of view. There is some scriptural support: 1 John 2:19, & John 6:37-40 for instance.
It is certainly possible to be a 'carnal Christian' -- redeemed, but living in unbelief. On their way to heaven? Yes. And yet, missing out on all that God has for them them here on earth. There's so much more to being saved than going to heaven.