2006 Sentra Power Steering fluid replacement/type

Southern NY
2006 Sentra with 116K on the odometer.

Replaced power steering fluid about 10K miles /3 years ago. Lately, the steering feels a little difficult on cold morning starts. The fluid doesn't look dark or smell burned. I wonder how often one needs to change the fluid. The manual doesn't mention anything specific.

If I am to replace the fluid, Nissan suggests using Genuine Nissan Power Steering Fluid (PSF) or, Genuine NISSAN Automatic Transmission Fluid (ATF), DEXRONTM III / MERCONTM, or equivalent ATF. I have some Nissan D-Matic ATF sitting around. I wonder if I can use that instead of PSF.

Thanks in advance.