I am planning on putting a fence up. I want to use 6x6 posts. I was going to dig the holes about 46-48 inches deep and put gravel at the bottom. I then intend to put a couple of bags of cement in and then just tamp dirt on top of that. Does it really matter if I get the .40 or .20 treated posts? I can't forsee a 6x6 rotting out in 15 years even if it is the lower treated type. I used 6x6 as corner posts for another fence I put in and cemented them in as I intend to do with this fence. After 5 years you could run a truck into those posts and they wont move. They were the .20 treated posts and I don't see any rotting whatsoever. I know the .40 posts are more expensive. I thought I was overkilling it by using 6x6s and then someone said you need .40 treated 6x6s. What would be the lifespan of .20 vs .40 treated 6x6s ? Thanks for any responses