Do what works for you bro, I mean if you're stll gaining big then keep it the same. I switch every workout so it's different than the last. ex, chest workout on saturday - Flat bench 5x5, incline DB's, Flies.... chest wednesday - flat bench dbs, decline bb, incline BB, arnold dips...... chest next saturday - flat bench maxout, decline bb, flies....... that's just an example of how i might switch it everyworkout. i do that with every body part and have real sick gains with all my lifts. Stimulating new muscle fibers and shocking your system will help you get big gains. try the 5x5 one week then the next week maybe go for reps or whatever. it's up to you