Tom Crotty, managing general partner of Battery Ventures, has today's best post of the day up over at PEHub.  It's titled The Portfolio Effect: Battery’s Tom Crotty on Why VCs Should Back at Least 25 Companies in Every Fund.  Tom explains that, regardless of fund size, each fund should try to have between 25 and 30 companies to get the right scale and diversity.  He doesn't talk about the time frame for the initial investments in these companies; we've concluded from our experience that a three year cycle of initial investment (e.g. the 25 to 30 companies get invested in over three years) creates the right amount of time diversity.