How long does it take to break in a nitro rc buggy?

I bought 2 new nitro powered rc buggy's and have to break them in how long does it take to complete the process how long does a tank of gas take to go empty and is it hard to break them in???

Thanks

http://www.youtube.com/watch?v=pAggkhHqEkw&feature=list_related&playnext=1&list=SPFB46144DF4EA109B

Is incredibly useful.