[TheLastSuperman]

Another alternative would be to not rely on such major third-party advertisers, if you don't have people banging at your door to advertise on your site then that might be your only option. If however you have quite a few people wanting to do banner style ads, you can include them by hosting the banners directly on your site and simply linking to theirs - some prefer to track impressions and clicks so then you could use the Rotating Banner System available here on the org OR Revive Ad Server OR Ad Peeps software if hosted on the same domain which will be less to load.

Quite a few options but when you're loading too many ads from third-party providers as others have noted above in previous comments those scripts must load and if too many or not optimized it's just going to take time, that much time though is just overboard. There always comes a point where you must decide when enough is enough, that includes ads and the time it takes to load your site. Everyone wants to benefit from ad revenue certainly but when it's in the way of the end-user loading the site in a timely manner and if it does not load fast enough they might close the tab/window because it's taking too long for the site to load, then your ads just failed in more way than one.