Landmarks are generated every hour, but I expect clients to pull them perhaps once or twice per day. Servers will keep two signatureless MTCs around a few days apart, so even if your client didn't update in a few days you can still use the small signatureless cert. The biggest reason for needing the big MTCs is for when you need a new certificate quickly. Our intern Lena had a look how common that would be, and she estimates it'd be required for 0.1% at any given time. https://www.youtube.com/watch?si=72ClhykaYDHf0sND&v=f8unMB2Q...