"Thousands" of inhabited planets are within easy reach of a Warp Five engine, according to Cochrane in "Broken Bow." Meanwhile, only 1 in 43,000 planets supports intelligent life - "Fight or Flight," and "thousands" of star systems lie along the Enterprise's path.
As of "Horizon," the Enterprise had visited 22 inhabited worlds.
By "Bounty," there's not one around for the next fifty light years while 6 light years from the Klingon border,
In "Regeneration," we see use of the term "Delta Quadrant" to refer to the origin of the Borg, confirming the early use of the greek lettered quadrants.
"Expanse" - the Delphic Expanse is 2,000 light years across. Coordinates within it are a three month trip away.
"Daedalus" - Vulcan is just over 16 light years from Earth.