Deadly Range is an ability the Sniper archetype gets at level 3. It is never "taken," and especially isn't taken more than once.
It increases every 3 levels, so at maximum effectiveness (at level 18+), it increases your Sneak Attack Range by 60' (probably to 90', unless you have some other abilities that also increase this range).
If you are referring to the Ninja Trick:
"Deadly Range (Ex): A ninja with this ninja trick increases the range at which she can deal sneak attack damage by 10 feet. A ninja can take this trick more than once. Its effects stack."
The answer is a lot....
in the Ultimate Combat book, under Rogue Talents:
Ninja Trick (Ex): A rogue with this talent can choose a trick from the ninja trick list. The rogue can choose but cannot use talents that require ki points, unless she has a ki pool. A rogue can pick this talent more than once.
Under Feats: in Advanced Players Guide
Extra Rogue Talent
Through constant practice, you have learned how to perform a special trick.
Prerequisite: Rogue talent class feature.
Benefit: You gain one additional rogue talent. You must meet all of the prerequisites for this rogue talent.
Special: You can gain Extra Rogue Talent multiple times.
so... once for each Rogue Talent, from level 2 on, and once for each feat from 3 and up.... for a grand total of 19 times by level 20.