Yes, it is. I admit there is sometimes a little compensation at newer episodes that I can't avoid, but I always try to be equally harsh at any Simpsons' era.
A 10 is not a top perfect score or something like that for me. It's simply what I consider for an episode that I liked too much and was nearly impeccable. And there are lots and lots of 10's in my book (I think they were at least 90). What makes the difference between classics and post-classics is that while the first nine seasons include approximately 80 of them, there are only 10 or less since season 10.
So, I am a high-grade user, but it is like that always. My notes are put on a scale that seems to be too much generous, but I try to be strict by giving any episode its deserved grade based on that scale.