Not every appearance of your main character in the movie needs a statement of his/her theme. Repeating a theme too often can very quickly become annoying or drift off into an unwanted comedic effect. In general, thematic statements are best placed when the character and his/her actions drive the story forward. Also moments that show off essential character traits (hero being heroic, villain being evil) are good moments for a statement of a theme.
Be aware that themes in general and also their extensive use have become a little old fashioned in recent film scoring styles. While it was perfectly fine to use them in practically any genre in the past, some genres (dramas, dystopian settings etc.) by now have a very distinctive tone that usually calls for a way more minimalistic approach, with thematic links being provided by signature sounds or minimal musical gestures or sometimes not at all. The operatic approach of thematic links has proven to be very effective in film scoring but is not the only possibility to support the narrative.