On Wednesday, July 26, 2017 at 7:40:49 PM UTC-4, sms wrote:
The brakes on my Specialized road bike were not opening all the way when
releasing the brake levers. At first I thought it was the old brake
cables having corrosion so I replace them, and I also put on a set of
new/used levers, since the springs in the original levers were weak, but
this wasn't sufficient.

Snipped
How often should I have to replace brake springs. Since this road
bicycle is about 30 years old I figure that the springs do fatigue over
time.

I think this is what I wanted:
http://www.ebay.com/itm/DIA-COMPE-S-PULL-BRAKE-PART-SPRING-/282571492776?hash=item41ca92cda8:g:LiIAAOSwUFtZaPk c

How often? NEVER! Just unhook each side of the spring from the caliper arm and then bend the brake spring upwards away from the caliper arm to increase the tension of the spring and you'd be set for many more years of use. The shop ripped you off by selling you new brake calipers you did NOT need.

Cheers