Qenya
inárea
as old as
inárea ní
as old as I am
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The correlative ᴹQ. inárea “as old as” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of the relative pronoun ᴹQ. i and an adjectival form of ᴹQ. are “day”.
Neo-Quenya: For purposes of Neo-Quenya I would instead define a neologism ᴺQ. yanaurë “on the day when” using the relative pronoun ya and aurë; compare Q. yallumë “in times when”. I would then use its adjectival form ᴺQ. yanaurëa for “as old as”, more literally meaning “of the same days as”. For example: nás yanaurëa ní “he/she is as old as me, (lit.) he/she is of the same days as me”.