Seeds and nuts are high in PUFA's. Heating PUFA's can oxidize them, and that is very unhealthy. Having said that, I still do it occasionally as part of baking. Flax is extremely high in PUFA's and should be avoided. Even though it is Omega 3's, it is the ALA kind which is extremely poorly converted to the forms that the human body uses. Other nuts are too high in Omega 6's, which pretty much require balancing with bio-available Omega 3's, again leading to too much PUFA's in the body. They also tend to be high in phytic acid which block nutrient absorption in the intestines. And finally nuts are highly calorie dense in additional to the inflammatory Omega 6's.
Occasional snacks can be gotten away with. The constant reaching and grabbing for nuts will set you back more than likely.