Don't hoard more than 15 points, or you will decrease your bonus. Take a look at this table:
Points Held
Bonus added
Total bonus
Percentage bonus
5
2
2
40%
10
2
4
40%
15
4
8
53.33%
20
2
10
50%
>20
0
10
<50%
As you can see, turning in 5 or 10 points earns you a 40% bonus, and turning in 20 points earns you