“....thus the examples you invoke simply have not kept their first love.”
But is the experience of “first love” by which we tell many Christians that you have “eternal peace” (in the sense of a known-security of one’s salvation). Are you saying that the loss of this love has no impact on their salvation?
Nope, because then salvation would be dependent on our efforts and it's not our efforts (or works if you prefer) but God's grace.
When we are born again, we are made new creatures in Christ, died to sin and the Law, and have been transferred into the kingdom of the Son He loves.
God doesn't disown us every time we don't meet standards we have set up for ourselves that we think God has for us.
People have this kind of mentality that if we reach a certain level of spirituality then we are good to go, but EVERYTHING about us is tainted by sin and cannot even come close to God's holy standards and level of holiness.
That we can somehow live a life that is acceptable to Him is an illusion.
And even if we could from this second on, live a life as perfect as Jesus did, it wouldn't be enough because it's already far too late.
One sin is all that it takes to damn us for eternity and the penalty for that sin is death. Doesn't matter if the rest of our lives are perfect. We already aren't and are disqualified for being able to stand in God's presence.
Your first question is unclear, but we understand Christians have Christ as their first love (used in Rv. 2), which results in obedience flowing out from that relationship, and which evidential fruit of obedience, "thing that accompany salvation" (Heb. 6:9) testifies to them possessing eternal life. 1John provides revelation and criteria by which one may know they presently possess eternal life. (1Jn. 5:13)
Are you saying that the loss of this love has no impact on their salvation?
No, it ultimately can have, as seen by my statement that "Scripture also warns of departing from the living, loving God by unbelief, and thus impenitent sinning. (Heb. 3:[6],12; 10:38,39)"