Zoey likes to play fetch but Magnus... not so much. Both love treats but as you say, it doesn't last too long. So to make it last longer, I do something like this:
https://www.youtube.com/watch?v=v711scxy4X4
And this is when I had to up the difficulty level:
https://www.youtube.com/watch?v=uHRf_NG1mzo
For Zoey, since she's so small, I just put the toy/treat ball under the blanket like this:
https://www.youtube.com/watch?v=5qVJ2Ax0QbI