So here’s a few things I think about when setting up carrier loops.
First off, the shortest distance from star to star is a direct line. Draw a line from the first star in a carrier’s loop to the last star, and the more the intermediate stars deviate from that straight line the more time is added. Now efficiency can be added with additional carriers, but even more could be made with those same number of carriers on more direct routes.
Second, figure out which direction you want your ships travelling. Never have your ships moving away from their eventual goal. Looks to me in that upper loop you have ships moving clockwise around a loop, so the ships from the star on the left move all the way to the star at the top before moving back down toward the central drop off star. Instead, the left star should have its own carrier loop directly to the central star (loop B) and the other two stars would get their own carrier(s) (loop A). Similarly with your loop on the lower left, it seems like ships are spending too much time travelling away (or at least not towards) their destination. Instead I’d have the two westernmost stars each have their own carrier looping toward the warp gate star, and the central drop off star would have its own dedicated carrier loop toward the warp gate star.
Thirdly, star industry levels can definitely affect how I set up loops. For example, say that middle star in the loop I labelled A generates 100 ships per day while the north-most star generates only 10 per day. I would probably start by giving the larger star a carrier or two to loop directly between it and the drop off star, The smaller northern star would get one carrier to loop to the larger. That would allow the higher ship count generated from the larger star to be collected more regularly without spending excess on carriers looping through both it and the smaller star each time.
Here’s another point with regard to keeping the ships moving toward (never away) from their eventual destination. If I have only allies to the west and south, and my enemy is largely to the north east, I’d make sure ships aren’t travelling too far away from the enemy just to reach a warp gate star; even if the trip is a little bit longer, it can be worth bypassing the closer warp gate star if it’s further away from the enemy, as in the diagram. In this case, I’d figure out if the trip back to the further warp gate, plus the probably wait time for another carrier to pick up the ships and go to the next warp gate star, would be more or less than just sending the ships directly to the next warp gate star.