I use the age adjustment for most additions, particularly after six months. I buy bulk leaf as fresh as possible, vacuum seal, and store in a freezer. Depending on the variety, not much adjustment for the first few months, but some varieties like centennial have a poor shelf life that you might want to account for. Using this technique, I have pulled two year old hops and obtained the results I wanted. No telling what the stuff in your LHBS is going to be like as most is not dated and storage is questionable. As a note, BeerSmith V 1.4 has a bug that adjusts all your hops to what ever date you use for one variety. Haven't tried it in V 2.0.