Lock sticking, jamming or just not as easy to use?
Believe me, its a sign that you need to do something.
It could be as simple as a service (you are servicing you lock with a graphite lubricant every 6 months and the mechanism is oiled annually)?
It may be a keep needs adjusting, a hinge needs a tweak or a gearbox strip down. These jobs are relatively simple to do but could save your door from breaking. You know it wont lock/unlock at the most inopportune time. and you will be faced with an emergency call out cost.
Let Dawson Sawyer Locksmiths repair these problems rather than replace.