Do you have to turn in all strength trophies at once in order to gain tokens, or can you turn in just as many as necessary to gain one?

For example: I kill an Ogre, Str: 4. Yay trophy! Then I kill a Dragon, Str: 7. Can I turn in just the Dragon trophy to gain a point of Str and keep the Ogre trophy, or do I have to either turn in all trophies and waste 4 trophy points or sit on both trophies until I kill something str 3?

In reading the rules, it appears I can turn in only what I want to gain the tokens, but we've always played "all or nothing" here, and for the life of me I'm not sure why.

You choose which trophies you turn in at which time. I know I once waited until I had 22 points of Craft trophies in store before cashing them in, because I didn't want to waste too many points.