The Borg are great and if they are real, I welcome our new overlords and hope for a position in the replacement of unimatrix 01. My methods will greatly add to the power of the collective if implemented well. Mighty Borg, I kneel before you and offer thanks.
So we've seen the Borg tear through species like they are nothing and then begin assimilation straight away. An example of this was in Voyager when the queen took Seven to watch an assimilation. It took only minutes for the Borg to triumph. In my opinion, this was a poor time to assimilate this species.
The Borg should always only assimilate a species when their technology is at levels that aren't yet able to overpower the Borg, yet also is good enough to provide a good amount of new technology. They also have to factor in their ability to control all currently known species to them and make sure their military resources are more than capable of defeating all of them in a situation of the highest probable projected amounts of simultaneous combat engagements. In other words, whatever the highest level of combat readiness they have to be at, is the minimum they should be at. They should also probably consider unforseen circumstances and even keep military resources a notch higher than the previously mentioned readiness level.
This kind of assimilation does in theory open the Borg up to a higher casualty count and loss of ships. However their ultimate goal is to be perfect. Preservation of all parts of the collective are secondary to acquiring perfection for the majority.
I believe the rewards from letting species "grow" further would far outweigh the concern the Borg would have over the increase in their losses in combat.
Do you guys reckon the Borg do assimilate at the right time, or they should wait?