It is easier if trains have similar travel times, so they return around the same time. If your 1st train is at level 10 then keep the others at level 10 as well.

At level 21, train travel times are reduced by 50% and take between 2h7m to 2h30m to return.

Trains are upgraded separately, and it is recommended that you upgrade them to level 21 as soon as possible.

The max travel time for trains is 5 hours, but it can be reduced with upgrades at the Academy of Industry. To change a train station skin, tap on the top-left button in the train station or tap the train engine and choose 'change skin'. You can see more information on the Skins page. The cost is less when the travel time is lower as shown on the Speed Up page. You can speed up trains to complete Regatta tasks sooner and to get construction materials if you are a few short.

Instead, you can also spend up to 9 T-cash to return trains immediately, which is less expensive. It is better to spend the T-cash speeding up the production of items in factories than to use cash to fill rail cars directly.

It is not recommended to use T-cash to fill rail cars because it is costly if you are missing a lot of the items.

What level is the mint in township