Yes, and no
For the most part your correct - you will not get a noticable change in battery life.
If you were to go to 30 minutes, from say 5 minutes. You might only get an extra hour - so for the most part - the phone being on, and staying connected with the tower will use the battery about the same.
If you keep the GPS hot, and keep hammering the chip - it will use it much faster.
But the change in refresh rate won't double your time. Does that make sense?