Bergers site has a great way to effectively find optimum lengths while still doing a minimum of loading (wasting bullets & powder)

http://www.bergerbullets.com/getting...in-your-rifle/

Typically if you've not seen any pressure signs at a given OAL then seating deeper will for the most part not nearly be as critical for pressure spikes as it would be if you were starting at a given point and then begin to stuff bullets.