Personally I think it a waste of money and space. I run my fans at 100% all the time. I prefer low temps over less noise. I have 14 fans in my system, including the 2 on my video card, one on my raid controller, 2 on the CPU, etc. You lose one 5.25" slot that can be used for 4 hot-swappable SSD's or an additional BR burner.
Did this help? No other responses seem to be forthcoming.
I thought I gave you points and closed it but I must have not.
I think I wont worry about it and keep them on like you say.
More money spent on better disk setup anyway.