FWIW, if by OSAS you mean 'once in the land always in the land', it is wrong. Even as Israel had to 'maintain' obedience to remain in the land:
Ye shall
walk in all the way which Jehovah your God hath commanded you, that ye may live, and that it may be well with you, and
that ye may prolong your days in the land which ye shall possess. Dt 5

33
,,,,so must the Christian 'maintain' obedience to remain 'in the land':
......to present you holy and without blemish and unreproveable before him:
if so be that ye continue in the faith, grounded and stedfast, and not moved away from the hope of the gospel which ye heard, Col 1:22,23
Behold then the goodness and severity of God: toward them that fell, severity; but toward thee, God`s goodness,
if thou continue in his goodness: otherwise thou also shalt be cut off. Ro 11:22
Now I make known unto you brethren, the gospel which I preached unto you, which also ye received, wherein also ye stand, by which also ye are saved,
if ye hold fast the word which I preached unto you, except ye believed in vain. 1 Cor 15:1,2
but Christ as a son, over his house; whose house are we,
if we hold fast our boldness and the glorying of our hope firm unto the end...... for we are become partakers of Christ,
if we hold fast the beginning of our confidence firm unto the end: Heb 3:6,14
OTOH, if OSAS simply means 'once regenerate always regenerate', or 'once a child of [the heavenly] Zion always a child of Zion', then yeah, it's spot on.