I have noticed that some people take a lot longer to pray than others. I was wondering what exactly adds to this length? I do understand it's probably thinking of the meaning of the words etc. but being that its davened so often, doesn't the person know what he is saying already? And wouldn't that familiarity reduce rather than lengthen the time needed?
The goal is concentration and that takes awareness and work. Some people naturally read slower but for many, it isn't a matter of reading as it is of focusing. The prayer isn't a race but a chance to connect with the divine -- it shouldn't be the goal to get through it as quick as possible -- that should be the opposite of the desired experience. It isn't about the holiness of the individual, but about the kind of religious experience that the individual is going for. We don't try to assess another person's holiness or tie it to our external sense of what they are doing.
If you had a chance to have a sit down with the president, wouldn't you measure every word carefully and speak slowly instead of zooming though some prepackaged speech? And if you had a prepared text, wouldn't you deliver it carefully, infusing into each word the subtleties of meaning and intention showing that yours is a conscious delivery and not a "by rote" performance? Actors on Broadway don't finish their plays faster just because they have memorized their lines.
The challenge is to keep it vital and fresh even though one knows what is coming next. Sure, in a pinch, someone very familiar with the words can rush through, but unless there is a pressing emergency or other valid reason, the effort should be made to pay attention to what each word means and carries with it.
Prayer used to be a personal liturgy, not a codified one. It has become established to help people who would not, otherwise, have the words to communicate to Hashem. We are still allowed to add in personal supplications and give the prayer even more meaning. But even if we don't, our job is to take the printed word and breathe life into it. And that takes time.
In my shul I am one of the slowest daveners, if not the slowest. One a good day kavanah will slow me down, but by far the most influential factor on my pace is straightforward pronunciation.
My spoken Hebrew is poor, but years of davening have made the words fluent in my mouth. Even so, I am careful to pronounce the words properly and it simply takes time to verbalise them.
Perhaps what I am doing differently is speaking loud enough to hear what I am saying, albeit in a whisper. When I can hear each syllable I am forced to slow down to make each sound separate and distinct. Not exaggerated, not extended, but not running into the next.
For me it's pedantry, not holiness.
At about 9 minutes into this video, R' Aryeh Kaplan, ZT"L, discusses how a meditative 'Amidah would be slower, and how this would afford the person praying the opportunity to connect to the Divine.
I think this question is based on a false premise that knowing the literal meaning of the words is equal to having kavanah. The question also borders on evoking a discussion rather than an answer that can be supported with traditional sources, however, I have a vague memory of a possible source that could address this question. Namely, our tefillah should be new every day despite the fact we're saying the same words. It requires thinking beyond the simple literal meaning of the words to make one's tefillah new every day, and that takes a little extra time. I can't remember if this teaching comes from a chassidishe sefer or the Talmud.
Addendum added later: I remember now. I got it from S'fat Emet on Parashat Ki Tavo, focusing on the pasuk Devarim 26:16, "Today, Hashem your God commands you to do these decrees..." There, he compares tefillah to bikurim (first fruits) because we suspend our typical human activities to take time out to engage with Hashem at the "first" opportunity. The idea of "first" opportunity relates to "reishit peirot," first fruits. He then expands the concept of "ha-yom," today, citing Rashi and Midrash Rabba on this pasuk where they say the Torah and mitzvot should be regarded as new every day. The S'fat Emet then points to Hashem's constant re-creation of the world and suggests that this is a hint to us that we have the power to make our daily service of Hashem new every day, and tefillah is the natural focal point for renewing our daily service to Hashem.
To respond to the original poster, I am suggesting that some people who take longer to daven might be attempting to engage in this mindful renewal of service through concentrating on the significance of what they're saying. This goes way beyond merely knowing what the words mean and what's coming next.
Additionally, some people who take a long time to daven may just be mindful of the correct pronounciation of the words. It actually does take a great deal of concentration and some extra time to make sure every letter is pronounced clearly, distinctly, and correctly, and that in and of itself is a new challenge every day. When standing before the King of kings of kings, it's generally a good idea to avoid carelessly mumbling and slurring one's words just for the sake of whipping through them as fast as possible.
Davening is about connection, we are during Davening connecting with Hashem.
When you try to connect with someone, it's not just about the words, rather it's about the feeling behind the words. The same goes with Davening, we try to not only understand the words but generate a feeling of love and fear of Hashem, this takes time.