If you’re running 1-2 lightweight, say Cat5 cables, you can get away with 4-5 feet between clips. At the maximum capacity of ~8 Ethernet cables, you’ll want to put them more like 2-3 feet depending on the situation.
The smaller 0.5 and 0.75 EMT clips are made to hold more like 3-4 cables each, owing to the lower strength of the EMT it’s being attached to. With the lower strength and fewer cords, you can estimate 2-3 feet between clips in those sizes as well.
For example, this photo is the EMT 1.0 clip easily holding 9 x CAT5e Ethernet cables. You can figure a pack of 10 clips will get you about 20 feet for that many cables. Even without the bands, they hold pretty well. And, unlike with tie-wraps, you can change wiring with No Tools and No Waste.
You can read more about this topic in the blog post Cables Heavy?.