1. If the film is close to being released or it has already been released, and you believe there's money to be made either way with respect to to box office gross.
2. If the stock is a high profile concept stock and there's no real downside to keeping it, i.e. you have the spare money. An example is in my other account that I no longer trade with, I actually had OMARS and CAPAM back when they were in the single digits per share. But I could spare the money back then.
The bottom line is as long as you think there's a sure profit to be made, and as long as you can't find a better place to put your money (like an adjusting star bond or weekend opener), then hold your penny stocks with confidence. However there are so many other ways to make money here, that with a few exceptions I think it's best to stay away from keeping your money in penny stocks long term.