This is one of those general questions that everyone wants an answer to, and somehow believes applies universally.
Everything in bodybuilding is relative to your individual genetics, hormone levels, and genetic response to certain things.
If you have a fast metabolism, do you think that the number of meals you need to gain size is the same number of meals a person with a slow metabolism needs to gain size?
Hopefully the answer is no.
The ideal number of meals to gain size is dictated by how fast your metabolism is.
Keep in mind, as you gain muscle, your metabolism increases.
The number of meals that were ideal for you to gain size a couple years ago, are not likely to be sufficient anymore as you now have a faster metabolism.
If you have a slow metabolism and start eating 8 meals per day because your buddy who has a fast metabolism eats that much to grow, you're likely to end up packing a ridiculous amount of fat.
Right now I'm at 220 pounds with 10% body fat and only eat 3 times per day.
However, this doesn’t mean that if you eat 3 times a day that you will grow adequately. You may need more, you may need less.
If I gained 40 pounds of muscle and was suddenly 260 pounds, do you think my 3 meals per day would be sufficient to maintain that weight or to grow?
Everything is relative and what works for one guy isn't likely to work for the next guy in the same way.