There have been so many times I’ve traveled and almost every single time I’ve ended up changing my return trip to extend it and visit another city or to stay longer in the place that I am at. And every time I regret that I booked my return flight.
So take a lesson from me and just don’t do it. In the long run it’s a lot cheaper and it keeps your options open. You can easily book last minute tickets and sometimes better availabilities or cheaper routes open up, although not always.
The cool thing is that you can do a search using Kayak to figure out which city has the cheapest flight back home and then take a super cheap flight using budget airlines like RyanAir or AirAsia. I still have not done this because I’ve continually made the mistake of booking a return and have been stuck, but this method is far better and allows you to keep your options open.
In short, go with the flow, don’t plan ahead and see where your travel adventures take you.