We'd already be flying space ships to other planets >_>.
Sex is remarkably good at slowing down everything since it is so powerful and alluring.
I'm all for Pon Farr if it means keeping our population down.
...the rest of the nine months would be boring as christ.
It would suck for guys, since the majority of mating seasons that I know of in biology are pretty much entirely on the part of the female: The male has the same sex-drive year-round, or only responds in response to the female's scent. The latter would be tolerable, but the former would really suck for straight dudes, unless the time of year was different for each female and didn't happen, say, ALL during the spring or something.
Here is the #1 thing to consider:
As is, pregnancy is 80% (or more) a mistake.
Very few people actually mean to get pregnant, so if we had a mating season it would mean people would aim for the best possible suitors at that point in their life and fuck everything else on the off-seasons. People aren't going to stop having sex, but it would pretty much eliminate accidental pregnancy, and force ugly people into extinction.
There would likely be two kinds of relationships; the off-season love, and the person you end up leaving them for (no matter how brief). Shit would be messed up, and people would start rationalizing that. "Oh, well I have to look out for my own personal interests. It is mating season after all... I'll be back in the fall after getting knocked up (or knocking others up)". The concept of 'leagues' will fuck us all over, as we constantly try to trade-up to something better once a year, and the people at the bottom will likely deal with that.
Aw man, I wish.
Then I could use my favourite game quote ever: "It was mating season, how could I've known she was your sister?"
blame it on the alcohol ;D
Any time we get horny is mating season. Females have a period of time each month where they are more fertile then usual.