Qenya
li(n)-
prefix. many
li(n)an
adverb. many a time, not seldom, several times, often, sometimes
linin-
prefix. many
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.
A correlative combination appearing as lian or linan “many a time, not seldom, several times, often, sometimes” in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/110), a combination of ᴹQ. li(n)- “several, many” and ᴹQ. -n(an) “times”.
Neo-Quenya: For purposes of Neo-Quenya I would stick to ᴹQ. lillume, since I think -n(an) was abandoned.