In our own solar system (sol), earth is one AU (astronomical unit) from the sun. It takes light 8 minutes to travel from the sun to earth, passing by two planets along the way. Jupiter is 5 AU from the sun, meaning 40 minutes of travel time at the speed of light. Saturn is about twice that distance, so that trip would take two hours.
I recall from somewhere that trade lanes in FL allow ships to travel at the speed of light within a solar system. I would venture a guess that travelling between any two planets via tradelane probably takes anywhere from 3 to 10 minutes, and travelling across an entire system probably takes one to two hours.
Why, then, would Trent take roughly two weeks to travel from Bretonia to Liberty? My guess is fuel limitations and frequent stops, most of that time he probably spent at stations or planets along the way, he wasnt flying in space constantly for that duration.
It could also be that jumps between systems take longer than we percieve due to time dilation from bending space. It could be that the 10~ second transition sequence from one system to another is really taking a day or more in real-time.