What's The Quickest Way To Tell If A Branch Is Dead?
Snap a small section: pliable and green means it's alive, brittle and dry means it isn't. A patch of canopy with no buds while everything nearby is leafing out is another giveaway.
Do Older Trees Carry More Deadwood?
Generally, if they haven't had regular attention - years without a trim gives more branches the chance to fail unnoticed, so an older, less-maintained tree often has more of it than one kept on a schedule.
Why Not Just Wait And See?
A healthy branch has some give in the wind; a dead one doesn't, so instead of bending it simply lets go, often with no warning at all. Over a walkway, a driveway, or anywhere people gather, that's a real risk worth addressing sooner rather than later.