I've probably had about two actual second homes and one metaphorical second homes in my lifetime.
The first one was from about the ages of 11-16. This new family moved into the street next to mine, and my brother and I became good friends with the two girls that lived there with their mum. There wouldn't be a week that would go by that we weren't around their house for whatever reason. It was normally to exploit their trampoline... but a good friendship did emerge based on non-trampoline-related activities, don't worry!
The second one was about two years ago, in my second year of uni. By this point, the friendship group that I was a part of had split off and living in two separate houses. As the academic year grew on, it became more apparent that the friends I was living with - while still great guys to talk to - were not particularly good housemates. So I ended up spending most of my time not at my own house, but at the house of my other friends, two of whom I'm living with to this day. The amount of times I was around there - and I did literally invite myself around on a number of occasions - led them to christen me their mysterious fifth housemate!
The metaphorical one would be the cinema, since I do go there a helluva lot of times. This week, for example, there's only been 2 days where I haven't gone... but normally I'll be there at least once a week. Fun times, y'all!