I did some calculations:
An USB with SLC NAND Flash can do maximum 100.000 write cycles. On an USB with 8GB with 10 MB/s write speed will that be:
(My math skills or not very good, I know for sure you can do this on an easier way)
((8192 / 10 )) * 100.000) / (365.242 * 3600 * 24) = 2.595945012206012 years.
So, when you write on your USB with 10 MB/s for 2,6 years it will be broken. Its true that it will be broken earlier. but when you have a good controller it will last very long. So yes, an USB with SLC NAND flash is a good option.
You also have SD cards on SLC NAND flash, but I don't know the technical details about the controller in the Raspberry pi, besides that. In my country an USB stick is cheaper then a SD card. So I bought a small SD card and an USB stick.
There is one downside, an USB stick needs power. USB can max consume 0.5 ampere. Model A of the PI has a limited USB power output, and not every power supply’s can handle that much amperes. So you need to check this before you buy an USB stuck for your PI.
“SLC NAND flash is typically rated at about 100k cycles (Samsung OneNAND KFW4G16Q2M) ” on the page: