I've seen guys get 10 to 15 and nothing happened. You need to first rebut the letter or file a grievance. Whatever is the practice in your local. A lot of letters are easily rebutted and are t worth the paper and in that they are. The reason they give these letters is it lights a fire under some peoples asses and they fall in line. Remember you can always give management their own letter and it's called a grievance. The grievance has over a three hundred dollar figure in there eyes for the time associated to them. Enforce your contract and the letters will go away.How many warning letters can you get before suspension or termination in a 9 month period or whatever it is?