I talked about this at a meeting last year and thought I'd bring it up again since I just noticed it again this morning.
We brewed an Imperial Brown ale on Saturday with an OG of 1.099. Take a look at the difference between the wort (via thermowell) and the ambient air in the chamber. The average ambient air temp (blue line) is 14C while the wort temp (green line) is 18.5C. That's a 4.5C difference, or a little more than 8 degrees fahrenheit!
I know some folks in the club control fermentation temps by measuring the ambient air. If you do this, be sure to compensate for the heat being generated by the fermentation itself. If you're one of those people, there's a good chance that if you had controlled your ambient air temp to be 18.5C (65F), it would have been fermenting at 23C (73.5F). That's quite a big difference. I've found that the bigger the beer in OG, the more heat being generated, which makes sense.
Anyway, I saw that this morning and thought I'd share. If you find your big beers seem to be a little hot, solvent, or having too many fusel alcohols; this could be your problem.