For those of you who know Lyle McDonalds, you can hate him all you want, but the guy knows a thing or two about nutrition.
While browsing through a number of his articles I've read one where he recommends eating a meal at most every 4 or 5 hours for effective muscle growth. I can't find the article but I'll try to find it and add it.
EDIT OK I found it:
Summary: Theoretical examination of meal frequency. It appears that eating too frequently could potentially be detrimental to the goal of gaining muscle mass in that muscle tissue becomes insensitive to further stimulation by amino acids, increasing protein oxidation in the liver. Eating more frequently than every three hours would seem to not only be unnecessary (based on the rate of digestion of whole proteins) but could possibly be detrimental. Given a moderately sized whole food meal, the body will generally remain in an anabolic state for at least five to six hours (and possibly longer depending on the foods chosen). Conservatively, we might use five hours as the upper limit cutoff for time between meals. This yields a duration between meals of anywhere from three to five hours. This should keep the body in an overall anabolic state without causing problems related to too frequent or too infrequent consumption of meals. Full time athletes with time to eat very frequently are probably best served with the higher meal frequency simply to ensure adequate caloric intake. Again, smaller individuals with lower total energy intakes may want to use slightly larger meals eaten slightly less frequently for practical reasons. Similarly, individuals who work jobs and are unable to fit in a meal every three hours needn’t worry obsessively about becoming catabolic. A solid food meal containing a high quality protein, carbohydrates, fat and some fiber eaten every five hours will maintain an anabolic state readily. >blockquote
I personally consider 3-4 meals/day a workable minimum for most, 3 meals plus a couple of snacks works just fine too. High meal frequencies may have benefits under certain conditions but are in no way mandatory. And, in case you missed it the first time through: eating more frequently does NOT, I repeat DOES NOT, ‘stoke the metabolic fire’.