An Argument Against Polyamory

Argument:

1. We have a limited time on this planet.
2. Time spent with one person cannot be spent with another person.
3. Intimacy takes time to develop.
4. (1+3) There is a limited amount of intimacy a person can have.
5. (2+4) More relationships, less intimacy all around.
6. (5+6) To maximize intimacy, a person should have one major relationship.

Counterargument:

1. We have a limited time on this planet.
2. * Time spent with one person can be spent with another person.
3. Intimacy takes time to develop.
4. (1+3) There is a limited amount of intimacy a person can have.
5. (2*+4) More relationships does not necessarily limit intimacy, provided time is spent in groups.
6. (4+5) To maximize intimacy, a polyamorist should spend as much time as possible in groups.

The key premises seem to be (2) and (2)*. Which is true to you?

What do you think?