Of course! There are LOTS of things that affect the efficiency! To be more specific, how old is your grain, how was it stored, and is it crushed or whole?
I had two bags from a bulk buy that sat unopened(uncrushed) in my garage for about 14 months. It is definitely dry in the garage, but it did get pretty warm in there in the summer. I was wondering if its age affected the efficiency because the last two brews I made using those grains (2-row & Marris Otter) had efficiencies in the low 60% when I normally get 72-ish%. Smell and taste test seemed fine to me.
Just did a SMaSH today with 2.5 year old Munich which was stored uncrushed in an air conditioned part of my house allowed to get as hot as 78 and as cold as 60. I got 86% brewhouse efficiency into the fermenter which for me is just a little low but still pretty damn respectable. Perhaps a few percent is attributable to age but not very much at all. 4% was left in the grain bed in the MLT and pretty much all the rest is due to incomplete conversion in the mash.