Depends on if you are following any particular protocol.
I am only familiar with a couple specific protocols; W. D. Kelley advises coffee enemas as an adjunct to liver flushing. He also advises multiple coffee enemas per day aside from Liver Flushing as part of his protocol geared towards getting people cured and recovered from cancer. Likewise, Hulda Clark - also geared towards treating terminally ill patients, advocates bowell cleansing to improve the results of liver flushing. I am not aware that she has stated an opinion either way on coffee enemas, but I haven't yet read all her books. Her bowell protocol is based mosly on herbs, supplements, enzymes, generally raising one's awareness on how to improve sanitation, and combination with flushes for kidney/bladder, parasites, and liver/gallbladder.
Edit: can't remember if I read it somewhere within the massive curezone forum, or elsewhere, but recently read a very interesting article that details how the Liver has it's own unique monitoring system (separate nerves, veins/arteries, valves, chambers, etc) that attach to the sigmoid colon. I'm probably botching the name but seem to recall it's called the 'entero-hepatic system'... ? The coffee enema (caffeine therein) - if done properly, stimulates and sends signals via this system which the liver responds to with dumping/releasing toxins. Was a very interestign read, I'll search for this article and post a link if I find it. One question it left me with - this article compared to similar ones, seem to be on disagreement on how high up into the colon the enema tube is to be placed. Some articles say up to 18 inches, others says only a few inches; undoubtedly there is enough disagreement on this to have significant impact on the success with the coffee enema.