Wear leveling needs free space to be effective. If there is only one sector of available storage, then that one sector is going to take all of the writes and wear. If the writes happen every 10 seconds on average, then the 5000-write lifespan of that one available sector would be less than 14 hours. I'm fairly sure the GRE scanners you mention lasted longer than that.
Automatic recording does impose a finite lifespan on the flash storage. You can estimate how long your storage should last with the following formula:
(Average time between writes) * (number of rated write cycles) = (expected operating lifespan of flash storage device)
I recorded some audio with my 436HP, and found that just over 15 hours of recorded audio fit in 1GB of space. So if your card has 3GB of free space, then your worst case average time between writes on each sector would be about 45 hours, and the card should last for just under 26 years of continuous use before write-cycle wear kills it, if it has a 5000-write lifespan.
If you're not getting that kind of life from your card, then there is some defect or other problem preventing you from getting the full rated lifespan of the card.
I appreciate all your and the manufactures theoretical information, but I call BS on all of it.
There is no way that 26 or 50+ years of service life has been tested on any of these products. If you frequent many of the photography forums there are all sorts of complaints of flaky SD cards, pro photographers are probably running the closest write cycle to these scanners and they are probably just a fraction of what the scanners do. These are all theoretical and calculated life cycles, not actually tested data and cards that are hammered on time and time again.
Lets talk in 26 years to see who's SD cards are still working. There are few electrical things that still work after 25, much less 50 years without issues, degradation or repairs. The only thing I can think off is the lasted over 50 years is 1950 spare refrigerator at my moms house that still works to this day. Has to be manually defrosted and it just keeps chugging away. I will likely find a spot in my garage for it at some point as it seems to have nine lives.
Out of all the USB flash drives I own and have laying around, I would bet I only have about 100 write cycles on them combined, so most flash memory gets very little usage. Even digital video cameras may continually or batch write to the SD cards, but I am not hearing high failure rate with video writing.
People do not use their flash storage like these scanners. I am not sure how Uniden writes to the the SD card, but if they do not batch write to the card and write every 5-10 seconds transmission, this is just a recipe for disaster.
I expect that faster and higher quality, larger SD flash cards may yield better overall performance in these scanners, but I expect to see continued issues on units that are recording on a 24 hour a day basis.