I will give a few verses that show olam does not have to be forever, Ps 143:3 , Lam 3:6 , Gen 49:26, Habakkuk 3:6, Due33:15 , Due 15:17, 1Sam 27:12, Lev 25:46, Gen 17:7, 1Kings 9:3. This is just a few verses , the verses that olam means forever or eternal are there but they are not even the majority from what I could tell.
Good on you! I spent the better of the morning reviewing every occurrence of "olam" in the O.T. I found 4 typed pages of vss. which define/describe "olam" as eternal, everlasting, etc. And I will post some of the vss. for the benefit of those who claim that "olam never means eternal," despite the fact that it is translated "eternal" in the 1950ish Jewish Publication Society [JPS] translation of the O.T. FYI the vss. quoted are from the JPS O.T.
Here is the equiv. of one page plus one verse. I have 3 more pages.
Psalms 37:28
(28) For the LORD loveth justice, and forsaketh not His saints; they are preserved for ever; but the seed of the wicked shall be cut off.
Psalms 45:17
(17) (45:18) I will make thy name to be remembered in all generations; therefore shall the peoples praise thee for ever and ever.לעלם ועד
Isaiah 51:6
(6) Lift up your eyes to the heavens, and look upon the earth beneath; for the heavens shall vanish away like smoke, and the earth shall wax old like a garment, and they that dwell therein shall die in like manner; but My salvation shall be for ever, and My favour shall not be abolished.
Isaiah 55:13
(13) Instead of the thorn shall come up the cypress, and instead of the brier shall come up the myrtle; and it shall be to the LORD for a memorial, for an everlasting sign that shall not be cut off.
Isaiah 56:5
(5) Even unto them will I give in My house and within My walls a monument and a memorial better than sons and daughters; I will give them an everlasting memorial, that shall not be cut off.
Jeremiah 23:40
(40) and I will bring an everlasting עולם reproach upon you, and a perpetual עולם shame, which shall not be forgotten.
Jeremiah 31:40
(40) And the whole valley of the dead bodies, and of the ashes, and all the fields unto the brook Kidron, unto the corner of the horse gate toward the east, shall be holy unto the LORD; it shall not be plucked up, nor thrown down any more for ever. olam
Jeremiah 50:5
(5) They shall inquire concerning Zion with their faces hitherward: 'Come ye, and join yourselves to the LORD in an everlasting covenant that shall not be forgotten.'
Jeremiah 51:39
(39) With their poison I will prepare their feast, and I will make them drunken, that they may be convulsed, and sleep a perpetual sleep, and not wake, saith the LORD.
Jeremiah 51:57
(57) And I will make drunk her princes and her wise men, her governors and her deputies, and her mighty men; and they shall sleep a perpetual sleep, and not wake, saith the King, whose name is the LORD of hosts.
Ezekiel 26:21
(21) I will make thee a terror, and thou shalt be no more; though thou be sought for, yet shalt thou never עד־עולם be found again, saith the Lord GOD.'
Ezekiel 27:36
(36) The merchants among the peoples hiss at thee; thou art become a terror, and never shalt be any more. עד־עולם