I have fond memories of the old K class steam engines and from time to time the long over night journeys from Otaki to Auckland and back. It was common to see the conductor scanning the platform for stragglers. They waited patiently for the late-comers: boarding at the last possible moment as they kissed a spouse or fare-welled friends goodbye.
Just as the conductor was patient with people boarding the train, God patiently waits for people to come to know Him. Yes, there will be a return by Jesus someday, and the heavens and earth we know will pass away... and it will be too late to establish a relationship with God.
But in the meantime the Lord is long suffering towards all His creation, not willing that any should perish.