But regardless of that, I think you are putting too much weight to the book. if you have DMed for years, and you read this forum regularly, chances are you're actually more experienced that the people who actually wrote the manual. And those people were writing most for inexperienced players anyway; it is assumed that experienced players will know when to bend the rules and when to skip them entirely.
I've never cared about numbers of encounters and I always went with what feels right for the world. The goblin tribe won't be conveniently divided into 4 easy encounters. After they sent the first group and you dispatch them, either they send every single able-bodied they can into the fray, or they flee. The boss won't send his minions against you one at a time before facing you solo at the end. he will either try to overwhelm with massive force; or, in case he's trying to wear you down, he certainly will try to prevent you from fleeing to rest and come back the next day.
I almost never had a standard adventuring day of 4 encounters. there was generally one big fight as the enemies would pile up everything they had. especially since the party learned teleportation, at which point taking them by attrition is an exercice in futility. Perhaps there were easier encounters, but i didn't even roll those. easy enemies surrendered, or tried to flee, or were killed easily. And it worked well.
Now, I'm not saying you should do as I did. of course everyone is entitled to have a different style.
But I am saying that you could benefit from more spontaneity and less slavish aderhence to a bunch of guidelines that were made by people with less actual experience than you, with premises that do not apply to your table, and that were never intended to be strict in the first place.
As for difficulty, as others said, it's up to the table. Some people enjoy different levels of difficulty. But in my experience, a party with even a fairly low (by this forum standards) optimization will still mop the floor easily with things well above their EL.