Shoulders and other joints are always tight for a reason. After too many years of tightness and/or pain a fellow aikidoka referred me to www.egoscue.com
. You can either find a consultant near you or buy Pete Egoscue's book Pain Free to start working through the issues that cause the shoulder tightness and start getting relief.
It has transformed my life and is what will allow me to continue training hard well into my sixties. I think it's very complementary to aikido.
The only drawback to egoscue's system it is it does take time. I try to do aikido every other day and my egoscue menu on the off days.