I am very worried and perhaps I shouldn’t be but want the thoughts of others and there seems to be many knowledgeable forum posters here.

2014 SR5P. Part-time 4WD. 130k. All stock. The last two front and rear diff changes I have done, there has been more of the fine particle collection on the front diff magnetic drain plug when compared to the rear diff. (No course particles seen only fine). I only use 4WD in the winter when conditions warrant. My understanding is that the rear diff/wheels propel this vehicle except when you use 4WD. I would think based on this that more wear particles would always be attached to the rear diff mag drain plug if I am changing both front and rear diff fluids at the same time. If this is the case why would I have more wear particles on my front diff mag drain plug? I change my front and rear diff fluids every year regardless of miles (overkill or a waste many will say). I do zero towing. Each change I will also keep drain and fill plugs out and run a quart of fluid through to remove anything the drain didn’t. Then of course would torque drain plug closed, add correct fluid amount (how service manual says to check level). I use Amsoil Severe Gear 75-90. No strange noises in 2WD or 4WD up front. The needle bearing failure rates in 5th Gen are very high from what I’ve read even with no mods for part-time 4WD. Maybe start of this? But again no odd noises or vibrations. Something worse? Would appreciate any thoughts or advice.