Your premise is incorrect. The assurance of salvation exists following baptism, and/or following sacramental absolution of sin, till a mortal sin is comitted.
If you wish to caricature this as ping-pong assurance, you may. I would, however, add that for a good Catholic avoidance of mortal sin is quite achievable, because he draws on the grace of God weekly at Mass and is strengthened by the Eucharist. While many suffer through recurring setbacks, just as many have a successful life journey on their way to sanctification.
I recall discussing this before.
Your premise is incorrect. The assurance of salvation exists following baptism, and/or following sacramental absolution of sin, till a mortal sin is committed.
My premise is that in Catholicism "assurance" does not mean "to be sure". Instead, and notwithstanding your explanation that avoidance of mortal sin is achievable (but how many succeed?), it really refers to a temporary or fleeting state. One can be absolutely sure in a particular instant, but have no assurance concerning 5 minutes from now. To me, that is no assurance at all. There is no sense of certitude that would normally be associated with a word like "assurance". In Catholicism, it seems more like an uncertain "hope".
I'm having a similar experience in my discussion with Joe about the meaning of "eternal life". He has explained to me that having "eternal life" does not mean that we will have life with Christ eternally. Instead, it means that we will have Christ with us as long as we abide in Him, but that we can lose "eternal life" at any moment, based on our actions. Again, there is no certitude about the word "eternal", it is only a "maybe". Just as above, "eternal life" seems to be more of an uncertain "hope".