Now we're going into the final six episodes. It's time to do our penultimate tally of all the arc focused episodes. Now, let's get some things out of the way.

1) Yes, I am aware I didn't mention the castle. That is because, unless the castle is shown in the show that it has relation to the chest, I am not counting it as such. If, however, there is a connection, I'll include it in the final imaged tally and in an unofficial counting in this description.
2) The Y/M sign relates to the shiny objects that the ponies get, which are implied to have some connection to the chest.

Tallying up, the ratio of plot:filler episodes is 7:12 (not counting the castle), 9:10 (counting the castle).

Hm… Come to think of it, including the castle might help make it more of a plot-based season.