> is the regular PLA limit of ~55 degrees Celsius not okay for a desktop accessory?

Not the author, but PLA has a glass transition temperature of around 60 degrees, which in layman's terms is when it starts to melt. However, depending on the quality of the printing process, layers start separating/the print is pliable significantly lower, at around 35-40 degrees. This means that in countries where you get 30+ degree summers, PLA is not really suitable for anything which experiences any kind of stress. I would hazard a guess that the standing laptop can cause quite a bit of stress when the train starts/stops.