What you don't want, is to use a wore key in the various tumblers. Look at your keys and notice the thickness. They should be uniform thickness at two levels. There should be no waviness or rounded edges. As they round off the very small tumblers do the same and eventually the tapered steps wedge beside the tumbler instead of lifting. This may only reduce the height that the tumbler is lifted but the improperly lifted tumbler then wears the inside of the cylinder and itself.

Keys are cheap compared with tumblers and labor!!

BTW the door handles are easy to recode or repair as they disassemble quite easily. With the tumbler barrel out of the lock and the key inserted one can see how the individual tumblers are pulled into alignmenmt with the outside of the barrel. In that position the lock turns. If a tumbler doesn't retract fully due to wear. One then files the offending tumbler down till the barrel is smooth with the key inserted. Massively defective tumblers can be just removed and thrown away as the new keys have a whole buch of tumblers. I have put old wore out locks back in cars with half or more of their tumblers missing. Only a real thief would know the difference and wouldn't care anyway.

On my vacation a few weeks ago to Aruba the only reason for a key was to tell which white Toyota Yaris was our rental, even a lock with many tumblers missing will still do that job.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician