I just noticed you're in Canada, and I got mine from maplerose.ca or you can also get them from babynaturopathics.com or waldorf.ca
Also we color in a sketchbook (just one from our art store) so maybe that's why we've not had problems with them.
I bought the 16-set Stockmar block crayons in a tin and my 3-yr-old uses them everyday. However, we also have the leftover pieces of a set of Crayolas, leftovers of Melissa & Doug triangle crayons, and a pouch of Crayon Rocks. I think the Stockmar's are worth getting a set because they do last so long and are natural. However, I would add a magical bag of those Crayon Rocks to your collection! They are made of soy and are specifically shaped to strengthen their handwriting muscles. However, they're soft and I don't see them lasting as long. But, they are cheaper. You can get the Stockmar crayons or the Crayong Rocks at Amazon, The Wooden Wagon, A Toy Garden, Magic Cabin, etc.
My understanding is that from a pedagogical point of view, the block crayons are intended for early elementary-aged children (grades 1-3) and are to facilitate specific coloring techniques. The book Coloring With Block Crayons by Sieglinde de Francesca is a great resource to learn how to use them and how to teach children to use them. She doesn't recommend direct instruction until first grade and says that young children can use whatever kind of crayon they want. She notes that some Waldorf educators feel that stick crayons are more appropriate for young children because it is easier to use them to draw the kinds of archetypal images that little ones usually draw as part of their natural development.
We have both block and stick crayons. My son, who is almost 10, really dislikes the blocks and even with direct instruction has had a hard time learning how to use them. He uses them for certain effects like if he wants to cover the entire paper to make blue sky or if he wants to make green or brown land. But that's about it. My dd who is six uses both, but mostly the stick crayons. However when she is in first grade in a year or so I plan to teach her how to use the block crayons properly and I suspect it will not be as hard for her as for ds. She is more artistic in general. At this point I just have all the crayons out in a basket and she can choose what she wants.
The block are more sturdy than the sticks, that's for sure. Even with my expensive Stockmar stick crayons, we've had quite a bit of breakage. With the blocks, they don't rarely break (unless thrown by some child in the middle of a tantrum). My biggest problem with the blocks is that my younger kids like to eat them. So I always end up with crayons full of bite marks.
I have 5 block crayons that I bought to try out and the only thing I don't like is that I stored them in a box with the stick crayons and they are all colored up now, especially the yellow. So if you want to color with yellow, you have to 'clean' it a ton by drawing on a piece of paper until you've drawn all the other colors off.
Does this happen to other people? How do you store them to keep them clean or do you not worry about it much? My son, who loves to draw/color rarely uses the block crayons and I wonder sometimes if it's because it's such a pain having other colors on them. I know I could store them separately but they are already all colored up from the other crayons and it's just convenient to store them all in one container so ds only has one container to grab when he wants to color.
The easiest way to get the crayons to not mix is to keep them separate in a roll. (see flickr link). This one is very fancy but it is possible to make it in 10 minutes with some felt folded over and a couple of stitches on each side the of each block. My 6 year old son made his own and he has fine motor issues.
I didn't understand the block crayons until I was shown how to use them properly. I copied a link for a "teaser" on how to use them. Good on you for trying to give your son such beautiful materials, it really does make a difference.
Waldorf teacher Steve Sagarin discusses block crayons and many other aspects of crayon coloring here:
I had the Stockmar crayons as a child, so I know their texture. That said, if you already have stick crayons at home, preferably a bin of broken ones, they're super easy to melt down. We had some tin heart shaped baking molds we got at the dollar store that were a touch too small for cookies - I was going to make soap with them, but anyway. I melted some plain old (and I do mean old) Crayola's down into the little heart shapes, and they came out great. They're not breaking at all and the kids can either shade with the sides, or make sharper lines with the hearts' tips. It recycled a bunch of nonusable crayons, and are a lot fewer pieces to keep track of than previously. Just a thought in case anyone feels like being thrifty.