Vanilla bean vs extract

I made a Vanilla Porter using 3 oz of extract in the secondary and it came out very tangy, but got much better over time (I only made 5 gal and it didn't get past 3 weeks in the keg).  The local brew shop suggested using vanilla bean.  I tried that on the second batch and it came out excellent from day 1.  But, over time the vanilla faded.  Does anyone have experience with extract vs the real thing to know if this is common and how to hold the flavor better with the bean?  I used 2 beans quartered for 3 days in the secondary and then added a 3rd bean for 2 more days.

I don't know if it would make a difference to the duration of aroma and flavour from the vanilla but I've added them to Scotch first and let them soak there for a week or two and then add all of that to the secondary. You could also use vodka, Amaretto, Bourbon...

I have never used vanilla extract in beer but I have had the same experience as you with fresh vanilla bean. after two or three months the vanilla aroma had faded quite a bit. the taste was there but not as prevelant as it was before. Perhaps a combination of the extract and the bean itself would help.