19 Wherefore it is neither wrong nor unprofitable to spend much time in praying, if there be leisure for this without hindering other good and necessary works to which duty calls us, although even in the doing of these, as I have said, we ought by cherishing holy desire to pray without ceasing. For to spend a long time in prayer is not, as some think, the same thing as to pray “with much speaking.” Multiplied words are one thing, long-continued warmth of desire is another. For even of the Lord Himself it is written, that He continued all night in prayer, and that His prayer was more prolonged when He was in an agony; and in this is not an example given to us by Him who is in time an Intercessor such as we need, and who is with the Father eternally the Hearer of prayer?
20. The brethren in Egypt are reported to have very frequent prayers, but these very brief, and, as it were, sudden and ejaculatory, lest the wakeful and aroused attention which is indispensable in prayer should by protracted exercises vanish or lose its keenness. And in this they themselves show plainly enough, that just as this attention is not to be allowed to become exhausted if it cannot continue long, so it is not to be suddenly suspended if it is sustained. Far be it from us either to use “much speaking” in prayer, or to refrain from prolonged prayer, if fervent attention of the soul continue. To use much speaking in prayer is to employ a superfluity of words in asking a necessary thing; but to prolong prayer is to have the heart throbbing with continued pious emotion towards Him to whom we pray. For in most cases prayer consists more in groaning than in speaking, in tears rather than in words. But He sets our tears in His sight, and our groaning is not hidden from Him who made all things by the word, and does not need human words.
Source: Letters (New Advent)