Personally, I didn't test my pet dwarves unless they showed signs of diabetes (especially needing to refill the water bottle more often, or a large wet corner), lost weight with normal teeth or developed bulgy eyes. Although it's not unpleasant, I didn't feel that it was worth putting them through it if they were well. I just avoided sugary/sweet foods as I do for my breeding/showing hamsters. I recently lost my last pet dwarf - a P@H Chinese who had been well for all of his 3 years and 10 months!
Regularly testing my breeding/showing hamsters isn't evidence-based but is the only other thing I could think of (as well as, of course, not feeding sugary things and not breeding from diabetic hamsters or their relatives) to try and stop diabetes in my lines. Even with regular testing I have been caught out by a male who was negative before mating but tested positive at the next screening when his pups were 3 weeks old
