trade routes

I'm playing in 18x18 galaxy. I have planets in sector 0,17 sending frieghters to AI planets in sector 17,0. That's 18 sectors x 12 grids = 165 grids long trip. At 10 grids per turn, it take my freigher 16 months to get there. When they finally arrive, the planet of origin is changed to one in sector 9,14. I was planing to put starbases along the route.
- Is there a max length for a route?
- why was the planet of origin changed?
- Why can't the info screen of frieghter show planet of origin?

Happy New Year!