There are all sorts of guidelines to consider. You'll disagree with almost all of them. That's fine. I'm going to tell you what works, after having worked on 200+ projects in the past decade, half with catalogers you know.
Contact Rhythm: If your annual repurchase rate is more than 35% and your organic percentage is around 50%, then an approximate once-every-three-weeks rhythm tends to be reasonable. Low repurchase rate brands need fewer contacts that cater to seasonal peaks. High organic percentage brands need fewer contacts because email is typically responsible for 50% of sales.
Larger Catalogs: You'll typically see a quarterly catalog with many pages, featuring a large portion of the merchandise assortment. These larger mailings happen at the start of a merchandising season (February, May, September, November). These mailings are not circulated deep, and for good reason. Larger mailings with many pages contain increasingly unproductive merchandise. Marginal segments become unprofitable segments as pages increase, so only circulate the larger page count mailings to the best segments.
Prospect Catalogs: Paired with the larger quarterly catalogs are smaller Prospect Catalogs. These catalogs have small page counts - and only feature WINNING merchandise presented via WINNING creative. That's it. There is no room for branding, no room for "making a statement", and there is no room for untested new items. Just the best. Tell the customer everything exists online. Prospect Catalogs typically generate 90% to 95% of the demand on half (or less) of the pages in the Larger Catalog, enabling co-op lists to continue to work.
Support Catalogs: A dozen or so catalogs with targeted merchandise assortments. In a Mens/Womens/Kids/Home framework, you might have 3 Mens / 6 Womens / 4 Kids / 4 Home catalogs - small page counts - only mailed to customers who have previously purchased or are highly likely to buy the merchandise featured in the mailing. Or, you have a dozen catalogs - each with a different "emphasis" - paginating Mens or Womens or Kids or Home at the front of the catalog. But again, page counts have to be down. There is no room in the future of cataloging for a monthly 180 page mailing - too expensive - and everything is already available online.
Dynamic Mailings: Only the very largest catalogers will dynamically merchandise pages via a plug-and-play strategy. One of the few competitive advantages catalogs have left is the ability to tell a story - and you cannot tell a compelling story via plug-and-play merchandising (i.e. mass merchandise personalization). Email is a much cheaper and more efficient place to execute mass merchandise personalization.
Stories: Look at the Orvis cover above - a whole catalog about dogs. Catalogs allow you to tell a story. Way, way, way too few catalogers are telling stories. Go look at a Lands' End catalog from 1991 for examples - or an old J. Peterman catalog.
Phone Buyers: These old-school customers get the majority of mailings, simply because the customer is pre-disposed to shop from catalogs. There aren't many of these customers left.
Desktop / Laptop Buyers: They're going to buy online, so why keep pummeling them with catalogs? Stop it! The typical Desktop / Laptop buyer receives between 3-9 mailings per year. Use email as the primary communication vehicle. Outside of twelve months of recency, it's 1-2 mailings per year, tops. If the lapsed customer visits the website or clicks through an email campaign, immediately send a hotline mailing. In fact, the future of catalog mailings is triggered hotline mailings. Nobody is talking about this because the whole discipline of catalog marketing changes when you realize that you trigger mailings only to those who are most likely to buy something right now. Trigger the highly productive prospect mailings to maximize response.
Mobile / Social Buyers: Catalogs are nearly irrelevant to this audience. 1-3 per year for the 0-12 month file, only triggered mailings based on website visits or app use or an email click for everybody else. Again, catalogs are nearly irrelevant to this audience. Measure your organic percentage among mobile/social buyers, and you'll see what I am talking about. Trigger the highly productive prospect mailings to maximize response.
Cost Savings: The catalog marketing budget is going to decrease by 5% per year, +/-, as pages decrease and contacts to online / mobile / social buyers eventually evolve to trigger-only tactics. The cost savings are funneled into online activities or other offline advertising programs - these activities are designed to generate awareness that makes it easier to acquire new customers at a low cost.