You always come up with fun topics, Ashley My answer would most likely be 5) 1 hour. Of course sometimes less is fun when  it's all about getting down and dirty for a satisfying 'quickie' But an hour seems to be a good ammount of time for foreplay as well as enough time for switching positions, which I love.

When is one truly satisfied?

If my ATF Piper is involved I would say forever but an hour or two is usually appropriate.

Never truly satisfied. Which is why we come back again and again and again. In other words we become your adoring  regulars !
)

Each round, that is!

Just as satisfying is the time in between each round to talk, laugh, drink, etc. that adds to the total experience.

I'm with you.....LOL  When I hobby, I usually do hour dates, so with some chat time, I guess the play time takes about 30-45 minutes.  In that time, I'm usually leaving a happy man.....

Swim

2 times in an hour and 3 times in 2 hours. Downtime for Caressing (or Massage) and Talking.
English is important

I like longer sessions with no rush.  I generally like to chat in between and take my time, actual go time?  probably 20-25 minutes each time with 3-4 times being the norm.

1 hour is probably good enough to make sure both of us are completely satisfied from foreplay to climax. But I'm a romantic and I'm a fan of spending several days together with that special someone and enjoying them in various stages of undress.  I might want to spend quality time under the sheets and then go to a club and caress her backside in her favorite "ass jeans" on the dance floor which leads to peeling those skintight jeans off as we molest each on the way back to the bedroom.

"Nature" intended homo-sapien coitus to last about 7 minutes

It is our wonderful gift(?) of reason & critical thought processes that brought about 60 or more minutes of foreplay.