Maybe it's the moods I was in, but the 2nd time I watched this Rifftrax I found it consistently hilarious & it's my favorite 2011 riff so far. I think part of what keeps the riff fresh is just what an eclectic film this is, veering from Anglo-Scottish period piece to 80's cop movie to swashbuckler to Queen music video. The whiplash from Sean Connery to Clancy Brown. It's given me more affection for the film than I used to have.
I recently admitted to basically the same thing, both in the rating thread and in the "Who's experienced Rifftrax fatigue" thread on the General topic board. Yeah, I wasn't a big fan of this riff initially, but after a break from Rifftrax and coming back, I liked it a lot more. And I agree, the eclectic nature of the movie definitely helps.