The problem is that we hardly ever see them use time travel otherwise. If Borg time travel science is as powerful as you claim, Species 8472 should have been no match for them, simply because the Borg would have warned their earlier selves not to bridge the two dimensions until they could withstand firepower equal to that of the regular bioships at the very least. Thus, it seems more plausible that Borg time-travel is either very difficult, very limited, very dangerous, or a combination thereof.marsh8472 wrote:There is of course no proof that a sphere capable of time travel has less capabilities than any other sphere which we know can go faster than light. Plus the enterprise was able to duplicate this technology to get back to the 24th century. You're arguing that the borg aren't capable of making the technology more compact than the enterprise even after acquiring all the knowledge various assimilated humans and thousands of other species.
If you want to see what a civilisation that really uses time travel properly is like, read Stephen Baxter's Xelee universe books. The Xeelee use time travel to ensure they are always the dominant force in the entire universe (well, except for the photino birds, but never mind them for now). If the Borg could time travel as easily as you claim, the entire galaxy would have been assimilated aeons ago.
Unless of course they miss something that then comes along to bite them in the arse before they can respond (ie travel back in time).They could also go back in time to where there was little sentient life and then get into the center of the star wars galaxy and proceed to travel forward in time until they find something evolved enough that's worth assimilating.
So the only times we see the Borg time travel is when there's a Borg Queen involved. How many do they have again ?Well actually a better reason is they decided to go back in time because the borg queen was aboard. Just like the borg queen was onboard lucutis's cube and she used time travel to escape in that situation too.