I have 2 Lexar 32GB Pro 1000x CF. One on each 5D III. Since photography is just my hobby, therefore, no backup for me. It almost 2yrs, no problem so far. No plan to update these at all.
I also have 2 32GB SD from sandisk. One on my RX1 and other will be used on RX100 II. They are 2-3yrs old. No problem so far.
The one I use on the 300D are 8 years and 5 years old and going strong. the older one is a SanDisk 1 GB and the other is a Kingston 2GB. The cards I bought with my 5D3 are just a year and a half old...
The 128MB card I paid about $100 for in 2002 for my first digital camera (a Canon S45) is still going strong in a digital picture frame I use as a night light. I expect that you're more likely to damage a CF card by removing/reinserting it than actually wearing it out.
Never had one "Wear Out", what I have had is where the capacity becomes too restricted for my current camera. My 3GB cards are sitting somewhere in a box, physically perfect to use, but lacking in capacity.
