I experienced your "puppy love", or as I would call it NRE properly in my late 40s. I had experienced it before but never really understood it or appreciated it.
This time I had my eyes wide open and was conscious though the whole process. I lived it to the hilt and apart from the polyamory aspect (I'm mono) was able to fully suck the nectar out of it .
I nurtured it and it has morphed into something just as wonderful but less frenetic.
Nothing amazing can last forever otherwise it wouldn't be amazing but if we appreciate every second of it that we can and nurture it then it can grow into something that is equally wonderful in a different way.