I wouldn't worry about that on this particular gun. it looks to be little used. The way I figure, a DR is very unlikely to break a spring considering how little use most of them see. Breaking a spring on an best shotgun is rare enough, and some of them have thousands of rounds fired through them. I'm not sure if recoil and overall use has any effect on the integrity of a sidelock's springs, or if the real evil is in the cocking action or leaving the springs under tension in the cocked position. Either way, 500Nitro is right, easy to replace and not very costly to do.
Also, bore condition is a good "guage" on how the rifle has been treated over its life. Good bores in a gun that shows otherwise a great deal of use on the exterior indicates to me that previous owners took the time to clean the bores properly and if they did that, they probably cared for and stored the gun properly as well.