Let Me Know if You Have Allison Transmission Fluid Questions

Tom: Can you please answer a quick question. My 08 Dynasty has a 3000MH that has a factory fill of Transynd. I had the Allison shop change the filters today. Unit has 35,000 miles. After the job was done the shop foreman asked me why I did not change all the oil. I didn't think it was necessary. He said it should be done @ 4 years due to moisture????? What do you think? Thanks

Moisheh