I had low expectations for this item, as I've purchased similar products in the past that did not cut very well and had low battery life. I used these for the first time this weekend to cut my Maltese X King Charles' hair after it had grown quite long over winter. The blades kept up with the thick hair, sometimes taking a few goes to get through it, but never jamming up. I used the length guide attachment to do the body, then removed it for the face and legs/paws.
It wasn't until about 35-40 minutes until I noticed the motor was starting to run slower, but after a quick hot-swap of the battery, I was back up to full speed for the last 5-10 minutes of the job. (My dog hates hair cuts, so it takes some time to get through the ordeal. :-))
These are also much quieter than other clippers I've used; certainly much quieter than my wired clippers. The blades are easy to clean and oil, so hopefully with regular maintenance they will keep sharp over time. (My packaging did not include the oil bottle as described, so make sure you have your own machine oil handy.)