cool post @pvoversc... I have had similar questions come up about this drive to find a planet - somewhere else - that is habitable... your colonization point would be quite accurate, I'm sure, if for nothing else than to exploit available resources - with greed being the driving force - as with all colonizations throughout history...
Also agree that we'd be better off focusing attention on this, our home planet. This is the only home we have and, it can surely survive without humans but, we humans can't/won't survive without it...
Need to start taking better care of Mother Earth...
RE: We can't stay here for ever...