I can't build colonizers fast enough for that to work effectively -- essentially, I'm trying to not have my colonies too spread out because I don't want my empire to be cut off from another part of my empire (ores, and so on, cannot be exploited by planets that are cut off from them -- you need a contiguous chain of planets). Each colonizer that I send to explore would mean one less nearby system I'm colonizing early in the game. Do you actually forgo colonizing in order to explore with that colonizer? And I would probably have to scrap my starting scout as well, because the bonuses are largely being triggered by the scout, and that scout pretty much has explored my frontiers before I can build my second colonizer. I think that the loss of getting that second or third system so late in the game because you decided to explore, would far offset any bonus you might recevieve by using the colonizer ship as a scout.