As you've discovered, the animated titles loop for a fixed length. If the duration is shorter than the loop, the animation doesn't finish; and if it's longer, the animation repeats from the beginning.
If tomasc's suggestion to create your own titles isn't what you're looking for, one way way to keep the existing title onscreen for a longer time is to set the title text then place it away from the other clips and add a color board to the track above it.
Choose a contrasting color for the best results. Play the title and stop it when the animation ends and take a screenshot. Note you may have to adjust the keyframes to keep the text at 100% opacity if it starts fading out before then end.
The you can place the screenshot on the timeline and chroma-key out the solid color. If there's a translucent section, you may need to play with the controls to get it to look just right.
Finally, place the screenshot on a track under the main title so that it starts before the active title ends. Here's a screenshot of the timeline showing the "frozen" title playing well past the active title's duration:
I've also created a sample PD18 project you can experiment
with. No need to sign in to OneDrive, just download it to your PC.