Originally Posted by The Batlord

This is the only relevant statement from your post. Yes, it is an easy mistake to make, but when somebody is actually reading your material it doesn't matter one iota how easy the mistake is, it just looks ****ty and makes the reader want to bail unless they're the kind of person who reads Twilight. No matter how easy those glaring mistakes are to make they should be cut out like a cancer because any reader worth their salt will see it as cancer. Prose is not something that gets an award for "good enough", it simply has to be good or **** you.