Do Mothballs Expire?

[Baldy's Boss]

I realized in my Green Victory game that some trains I had sent to depots years ago had gotten loose (and in the case of some engines whose obsolete wagons had been scrapped,running up running costs without any revenues).
I recall doing nothing to reactivate them.
Is there a maximum time that trains stay put?

[Sylf]

No. You must have accidentally ordered the train to be activated.

[Baldy's Boss]

In the case of some of them,the engines were of a model for which I ordered a blanket replacement.Would that result in new ones being built and sent on their way?

[Sylf]

If the train was already in the depot and stopped, then no, the replace order does not order that train to leave the depot.

[Eddi]

most likely you clicked the "start all" button (green flag or dot) in the train list at some point.