Well I don't know how true this is - but I believe having sex every day improves the quality of sperms.
The following text is quoted from a research article:
Regular ejaculation empties this sperm reservoir, making sure that newly produced sperm of higher genetic quality can get out.
Longer periods of abstinence, however, achieve little because while the quantity of sperm might increase, its quality declines. As sperm is produced, it is stored in the epididymis at the top of the testicle, but the longer it sits there the more damage it accumulates from exposure to free radicals.
To learn more visit this website and read the article:
http://www.timesonline.co.uk/tol/life_and_style/health/article2665788.ece