Prolong adverbs are provided in this article. The words listed here are commonly found along with the verb prolong in sentences. This reference page helps answer the question what are some adverbs that describe or modify the verb PROLONG.
actually
greatly
indefinitely
significantly
unduly
Hope this word list had the prolong adverb you were looking for. In addition to adverbs used with prolong, other example verb adverb pairings can be found on this site.
You can help by adding more adverbs in the comments. Thanks.