2,5 mg bisoprolol is a low dose.
Beta blockers do not shorten life. Rather, some research indicates that beta blockers reduce mortality, even without heart disease. They help reducing the effect of adrenaline on the body and lower blood pressure. As long as your heart rate or blood pressure doesn't get too low, and you're taking your beta blockers as your doctor told you to do, you're fine!
Noone is taking Concor? :(