Can we permanently conquer temptation in this life?
Temptation is something we have to constantly work against. I don't know of any fruit of the Spirit, or any virtue or act of obedience that—having been accomplished once with joy, success and power—is guaranteed the very next day, let alone the next year.
Sin has inertia that remains in the human heart. Every day the remaining corruption—which we must constantly be mortifying—raises its head and makes the successes of yesterday the challenges of today.
I picture the Christian life as an arrow that, rather than going straight up at 45 degrees with no dips, goes up and down, up and down. That's the way we live. There's a battle to be fought every day. And we must fight it in community.
We cannot rest on any past laurels. We must fight the fight of faith every day.