[LionofPerth]

Personally, I'd either go for the retirement option, get enough to own a life style and retire the character.

My other option would be, if you have that much money, start a business, grow it. Develop it, get business contacts, make even more money, defend the business from other runners and the like.Not just own a lifestyle, but be in the position of running something. What that is, is up to you.

Third option, combine options one and two. Retire the character to run a business, but work for that business as your new character. Help it grow and be active in its daily activities.

[Poindexter]

Dream up and set up the ultimate bug out plan, complete with fake SINS, vehicles, weapons, international contacts and all.

[Tarislar]

Actually OWN a lifestyle (100 months of payments) 

Until you have at least 3 of these, at the HIGH level, all on different Fake-6 or  your Real SIN.  Then you still have stuff to spend money on.