“...this must keep you quite busy...”
Romans 2: 6 ...who will render to every man according to his works. To them indeed who, according to patience in good work, seek glory and honor and incorruption, eternal life: But to them that are contentious and who obey not the truth but give credit to iniquity, wrath and indignation. Tribulation and anguish upon every soul that worketh evil ...
These people are told to work out their Faith. To obey is an action/a work. There is no guarantee once and for all that a person has attained salvation, Faith must be put into practice every day. Satan is in the world and is constantly tempting us to sin. Sinners who are still sinning without repenting are not saved.
“There is no guarantee once and for all that a person has attained salvation...”
Salvation is sure for those who have entrusted themselves to God. Christs life in them bears fruit. Where there is no life of Christ, there is no fruit and no entail life.