When we first brought Thomas the Tank Engine in our home, I purchased a number of second hand die-cast trains and gave them to Elliot. But it turns out that Elliot is pretty hard core about his train playing and wanted to be able to connect ALL OF THE TRAINS, which lead to much weeping and wailing and gnashing of teeth when he would connect too many of them and the line would break as he pulled it along the carpet.
So...sucker that I am, I went back to eBay and secured wooden ones instead. Though we've extensively grown
that collection as well and now he has a ridiculous quantity of wooden trains. But he loves them, so it's worth it.
But now that he has his wooden ones, when Paxton needs a train fix, he has the die cast ones to turn to, which he does.
Paxton is an extremely clever little boy. He figured out that the trains stay together if you put them on tile instead of carpet. Our little engineer!