RE: When do rotator cuff exercises?
This is my view, and i've read things to this effect but cant remember where.
if you are going through injury rehab then it is essential to strengthen the rotator cuff muscles in isolation (in other words exercises specific to RC), however if you aren't then traditional exercises working around the shoulder joint performed with good form and through the correct range of movement will be sufficient to keep these muscles in good condition. Bear in mind these muscles are tiny compared to most other muscles around that area.
i also see people using dynobands for RC exercises and in my eyes these can cause more problems than good.