I seriously doubt I'll ever get scores that high, but I'm willing to try new ideas.
In
this attempt, I tried the apparently popular idea of putting a dwarf star right next to the central star. I didn't even make it to 200 years.
In
this attempt, I decided to try putting a brown dwarf in the habitable zone. I added only one planet before deciding to not push my luck any further. I made it to 500 years.
Finally, in
this attempt, I put a dwarf star in the habitable zone, then one earth-size very close to the central star. I successfully reached 500 years and a personal high score of nearly 18,000,000. (Interestingly, the replay put the final planet a little further out, which ended up with a score much higher than what I actually got.)