King Daniel Into Darkness wrote:
TOS - 1000 LY in 12hrs at warp 8.7 ("That Which Survives")
VOY - 70,000 LY in 75 years at warp 9.975 ("Caretaker")
It also means that the original ENT could travel the entire width of the Milky Way in 50-60 days, making our Galaxy far too small for the purposes of the "expanded" show. Really the 60s show made warp too fast, Voyager got it right.
I once in a sadder moment used the chart in the Encyclopedia to work out how fast voyager would actually be going to do the journey in 75 years, an average of Warp 5 or 6 - which actually makes sense. If we imagine Stotti is bragging a bit, and take into account what other posters have said, then warp 9.975 is Voyager's equivalent of the Ent-D's Warp 9.6, they can keep it up for a while but then they have to stop or blow up. Also it is on screen in TNG that hammering around damages the engines (The Chase).
So Voyager could realistically at "maximum" average around Warp 5 to 6 on it's way home, this also ties in with travel times in general in TNG and DS9.
The newer shows and movies fudge this a bit, but you actually have to take things very literally to assume Earth-Kronos take "minutes", assuming a bit of time compression it certainly didn't take long, at most an hour or so, but we can safely assume that nu-trek does it's own thing!