How do i get my sim to reach golden anniversary?

Question

they have not cheated or flirted with any other sims.

Answer 1

Keep them married until they are old together  

Answer 2

This is what I found out:

1. The sim with the lifetime want of golden anniversary must reach elder status.

2. Have the sim with the LW make the phone call to throw an anniversary party (there is only one type of anniversary party).

3. There is debate on whether or not cheating/flirting can interfere with fulfilling this LW.

4. Make sure your party score is good (may or may not have an effect).

5. If it doesn't work the first time, throw another party. The couple may have to be married for a minimum of 20 sim days.