Yes, springs lose their tension/pressure with use. Newer springs have the advantage of better manufacturing, and they will be fresh. Valve springs should be changed periodically. They don't last forever.
Typically, a valve spring will lose about 10% of its pressure within the first few hours of use, and then settle in for the long haul at about 90%.
Most performance enthusiasts with high revving engines will change valve springs at least once per year. Regular motorists don'need to do that because they aren't pushing the springs to the limit.