How long is the retention period for keeping entry forms submitted for give aways, such as paintings, cars, etc.

Since most state laws govern lottery's/drawings/give aways, I would recommend consulting your state laws and regs, or state commissioners office for guidence on this.

I would imagine though that once it has taken place and been certified or your winner has been named and accepted the gift, you could toss them.

If your prize value requires a 1099, that may be a different retention period though.