Sort:  

People get new dogs over and over, building new relationships as pups grow, then age and die. Would relationships with other humans take on a similar cycle?

Possible, or probable. The latter I think as I believe the quality and strength of relationships are declining generally already, for many reasons I guess.

Absolutely G... So what if everyone else becomes immortal and we forever develop a better civilization, what are your thoughts on that though

I don't think civilisation is getting better, just worse. Humans will be extinct eventually, it'll be a good thing for the planet.