I average 9ish and I very rarely see 2 pairs in inspection. You're probably just mistaking good lookahead for something that was completely planned during inspection. If you plan out cross+pair in inspection, then as you are doing that you can notice other pieces that could be used for the second pair.
How to go about planning more than just the cross during inspection, which I believe is your main question here, really depends on how far along you are. If you're not very experienced, it'll just be too much for your brain to calculate during <15 seconds. As you get better at cubing in general, your ability to track pieces forward (see where they'll be after the next few moves) will improve. There are techniques to practicing this specific thing, but until it becomes the biggest thing holding up your times, there are better things to practice.
One way to improve this part of your solves is to take as long as you want to inspect, and just plan out the cross. Then solve the cross without looking. Keep doing this until you get consistent. Then limit your inspection time to, say, 30 seconds. Get good at consistency there. Push the limit down until you get to normal inspection times. It's also good to watch some tutorials on efficient cross building. Solving the cross one piece at a time is not viable for speedsolving and very inefficient.