How often to change the oil?

:
mazda
Since I bought from a dealer, I drove 3.5k on freeway (99%).
Fluid color looks very good on inspection.

Manual says 7.5k for my kind of drive - or 5k otherwise.
Dealership put a sticker to change in 3k

Oil is also 1cm higher from the upper hole on the dipstick.

When I change, I will be using Mobil 1 - assuming same kind of driving, how often should I change? What is if I do 3k to 5k per yr.
 
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