Daytona Power Reserve

[viper123]

I've a Rolex Daytona (116520). About 1 year old, bought new from an AD.

The power reserve is working out to be about 36 hours max. According to my manual and what I knew (or though I knew), the power reserve is meant to be about 72 hours.

Just took it to my local AD today to have them look at it and they told me that it's meant to be 36 hours.

Can anyone shed any light on this?
Is the AD right, or are they misinformed?
If my watch does have a reduced power reserve, what might be causing it?

They've taken it in and are doing an examination, but I'd be interested to get feedback on this. I'll know the answers from the workshop in a few days, so I can update this later - but would still love feedback in the interim!