I lost 2 OFers (starting CFer then the guy who replaced him) in the same year to CEIs. I don't remember what the first one was, but the 2nd was a concussion. I'm in my 5th year and those were the only CEIs that I've run into on my team so far.
I will admit to editing injuries that happened a few days before playoffs were supposed to start because I was too lazy to bench my best players for the last series of the year
. Bottom line, it's your league so do whatever is the most fun for you.