In any particular believer, assurance isn't assured, but it is assuredly available. God's promises in scripture tell us that we may have assurance, but that doesn't mean that all believers apprehend this truth. It doesn't affect one's salvation, but it is a gift from God to those to whom He reveals it. I am sure there have been some who professed assurance and then lost confidence. We all have moments of weakness from time to time. But again, it doesn't affect salvation. I am also sure there have been some to profess assurance and been wrong. They were never saved.
I'm not sure if this is sophistic or not, but if assurance isn't assured, how can it really be assurance?
I guess, answering my own question, some assurance or a sometime assurance would be better than none in the Protestant view?