The Reserve Electronic Warfare Squadron in Kingston had 10% reg force personnel in it when I was there in the 90's. I thought it was a very effective mix, and brought disparate strengths from reg and reserve together. In 95 several of the reg force pers got posted out without being replaced, so we became a 5/95 sqn instead of 10/90. The net result was a couple of extra class B opportunities for reservists to work on day staff, and I don't think the unit's effectiveness was diminished at all. Over the long term though, I think it would be detrimental not to have that infusion of new ideas and experiences every posting cycle. I didn't stick around for the long term (I left in 98), so it's hard for me to comment beyond that.