How long should I wait to get a new phone after its release?

So my iPhone 5s doesn't work anymore becauseit fell into the sewer and I've been using my old Nokia from 2007 and I'm wishing for the release of the iPhone 6S. I'm 25 years old and I'm on a budget especially since I'm still in college. I don't want to buy it right away because I know how hectic it can be and its a better way for me to buy it when the price drops even a little. I'm planning to get it on Black Friday so it will be cheaper. Hopefully I'll get it by the year ends. Thank you for your understanding.

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