College Senior Considering Taking GMAT (Need opinions on studying strategy)

I am a senior at a public ivy entering management consulting as an entry level associate. I want to have the flexibility to enroll in an MBA program, and not have to worry about studying once I start to work full time. I have a few questions for anyone that may have been in a similar position.

1)When should I start studying? -I begin working this fall so I will have the full summer (ideally taking the exam late August to mid-September)

2)Is there any harm to studying now? (I will only be studying 1 maybe 2 times per week) -I have a relatively full course load my final semester and will not be able to intensely study until late April-early may.

3) Should I wait until the summer to start?

4) Is its ok to study "casually" throughout the next few months and then intensify once i graduate.

-I am an economics major with a target score of 720-730

Any insights at all would be much appreciated!