I normally only take short drives but I just completed a 2100 mile (mostly highway) trip. This was my first long drive with my CX-5. I can honestly say that I never felt the lane keep assist nudge the steering wheel. Everything was turned on and the lane departure warning worked perfectly. I'm comparing this experience with my 2019 Subaru which quickly takes noticeable corrective steering action. (Not necessarily a good thing).

I believe Mazda takes a different approach. After considerable on-line research it looks like Mazda does nothing if it detects that the driver has a firm grip on the steering wheel. We also know that you can't test the system by letting go of the steering wheel because you'll get a quick warning message to hold the wheel. I can't find the design philosophy described in the manual but there are several online videos created by various Mazda dealers that suggest this concept.

Here's an interesting passage in the manual. Page 4-162 (pg 316 in the PDF)

The distance and warning sensitivity (likelihood of a warning) which the system uses to determine the possibility of a lane departure can be changed. Refer to Setting Change (Personalization Features) on page 9-12.

This suggests to me that you can increase or decrease the sensitivity of the lane keep assist activity. Change to HIGH for increased activity or LOW for decreased activity. However, the instructions for setting this level seems contradictory to me. Take a look at page 9-13 (pg 685 in the PDF)

The cancel sensitivity of the steering assistance for the system can be changed.

To me this implies that high sensitivity causes the system to cancel more (activate less). The default setting is HIGH and that is what I used for my long trip.Perhaps if I had the sensitivity set to LOW, lane keep assist would have occurred.

I'm interested if the community has any experiences in this area.