Well believe me when I say I tried EVERYTHING before I got to the right thing. I looked at:
Final E in grid in clues, Final Y in grid and clues, Final ly in clues, Things that went on or lasted forever (like Pi, the Messiah, Dvorak symphonies, characters voiced by Mel Blanc), PI and PIE RA and SRA (since you seldom do two letter answers I was suspect), Words with "ON" in them to see if there was ON and ON.
FINALLY (yes, reference intended) I went back to my forever idea and while looking up the half life for scandium (and finding it to be hours instead of eons...stupid non-radioactive isotopes) I went back to SCANDIUM again and instead landed at SANDPIT. "Idiot" I proclaimed, but I saw how I could do that since it had an AND in it....WAIT A MINUTE NOW! So there were a preponderance of ANDS, plus they were symmetrical; clever boy Ben. Of course my first answer AEPOIMIL (which Webster's defines as "Inability to solve a meta crossword despite having the right idea") was wrong but "ultimately" I saw my way home. Now here I was going to say, and finally - and then go on for another paragraph or two, but instead I'll just say "Thanks for a puzzle with long lasting enjoyment"