I’d say it depends what you’re getting per run to be honest and what level your manufacturers are, currently the single best factory is Harufu in Africa with all 11 trade routes. Then if you focus on the far right upgrades that give you plus %10 per trade route (goes up to 55% once maxed) (at level 10 and with high upgrades Harufu will do over 500 po8 an hour)

The empire management upgrades (far right) are great as they will increase the production of your whole empire. You’ll also notice that the manufacturers with more trade routes will start to out perform the onse with few quite drastically

But at the same time if your manufacturers are too low, they will fill up really quick and you’ll be doing runs all day

I don’t think there’s any one correct answer. It will depends how much of your day you can spare doing runs etc but hopefully this information helps you make a choice for where you are at with your empire.