No one can hold contest conditioning after a show for a relatively long period of time. If someone goes from lets say 4% BF and has about 6 months till their next show or even a year, you are naturally going to have a rise in BF. The key is to stay around 10-12% all year if your goal is to compete. A person can put on as much, if not more muscle at a lower BF than at a higher BF.
I see what you are saying about training heavier, but this is BBing not powerlifting, I personally don't fall into the category that heavier is best as opposed to greater volume. Heavy usually means more susceptibility to injury, all you need to do is take a look at all the injuries most have suffered due to poor mechanics and heavy loads. If you tear a muscle your out till you heal but smart training = longevity and greater gains.
When I say heavier, I don't mean singles or doubles or triples, although you can do them if you want. The risk of getting injured is the same as when you are training lighter - you just need to make sure you use proper form, ROM and all that.
I train basic, free-weight compound movements all the time and I do triple drops on nearly all of them, except for the deadlift. I do about 4 - 6 reps on the first set (to failure), drop it down and blast out another 6 - 8 (to failure again) and drop it down one last time to do about 10 - 15 reps. I've been doing this for nearly 12 years now (on and off).
Injuries are common to everyone who lift weights - I'm talking lifting as in putting in a decent amount of effort and not just doing 12 reps with a light weight before setting it down and moving on to the next machine. I see all the guys who keep saying I shouldn't go heavy and guess what? They are all skinny, with no mass or density. When you train heavy, it shows in the way your body looks - thick and dense, as opposed to looking like a swimmer.
Not saying everyone HAS to train like that, but if you are natural, there is no way in Hell you are going to increase your size and muscularity without trying to constantly increase the amount of weight you do - in other words, progressive overload / resistance. Volume is more of an ancillary variable, since you can do high volume with light weights and unless you are juicing, that technique isn't going to get you any size.