I recently added oak soaked in bourbon (1month soaked) to a RIS. I used 1oz of soaked cubes and .25oz of fresh cubes. I chose not to add the bourbon, but kept it in a jar to add later if needed. I ended up keeping the oak in for about 2 months. When i reached approximately what i wanted from the oak, i left it in another 2 weeks. I did this to account for some fading since the beer will age another 3-6 months before serving.
I have done a number of Oaked stouts and bourbon soaked oak as well. I soak the oak cubes till they are all sitting on the bottom of bottel or about 2 months. 2oz of American med. is what I have done. I have a Bourbon Oaked Russian Imperial Stout sitting right now can't wait to bottle it.
Keg1 Vanilla Coffee Milk Stout
Keg3 Gereman Rye
Keg4 Robust Porter
Keg5 Dark Saison
Secondary 20gal Black Imperial IPA , Belguim Wit, Apple Wood Smoked IPA dry hopped w/ Citra