Polaris OEM springs have a tendency to sag over time. In my opinion it’s always worthwhile to upgrade the springs. Also, the less the preload on the springs the better. Too much preload trying to regain ride height can cause shock damage by slamming the end at full extension. It’s better to go to a heavier spring and keep less than 1” of preload while maintaining proper ride height.
Also, proper ride height is based on shock travel, rather than axle angle. I’m assuming you got Rhino Axles with the long travel, and they can handle all the extremes of the articulation angles allowed by the suspension. With factory spec being 14” ground clearance on 30” tires, and assuming that SATV Long Travel maintains the factory shock Geometry, the ride height should be set the same (with adjustment for larger tires) to maintain the best shock performance and ride quality.