Right now leveling Builder is pointless past level 30 for the most part other than just the job income. 5 Minute fly usually is pretty limited for larger scale builds. I think added an extended town fly for level 40 and 50 would make it more worth the time and effort and grind to get to that point.
Examples:
Level 40 Builder: 8 Minute Town Fly
Level 50 Builder: 10 Minute Town Fly
Examples:
Level 40 Builder: 8 Minute Town Fly
Level 50 Builder: 10 Minute Town Fly
