Have a less than a year old Libery safe with mech tumble lock.

Lock had been working fine for months.  Then Sat, it refused to unlock.   Did some tapping with a rubber mallet at points the tuber's said to
It finally "caught" and unlocked.  Took the toys out just in case.  Of course, with the door now open, spin the tumbler and it is back to no unlock.

Had stuff out but unsecured, so spent a few days until Liberty could get a new lock to the shop I bought the safe at.
Tech finally comes out, declares the wheel for the last number had slipped a couple!!  Theoretically, if I had tried up and down a couple numbers for 3rd, would have opened.
Brand new safe and lock?  New lock in (not sure just how new it was, parts loose in styro peanuts) and it works again.

All this time, was convinced mech tumblers were the fail-safe but slow way to go.  No EMP worries, etc.  What a wake up call.

Lesson:  If any of your mech lock numbers start being "touchy" might get a safe or locksmith to check out if all the wheels are in line and not starting to slip.

I am starting to think about getting a Securam Prologic that is supposed to be hardened against EMP.

No type of lock is perfect.  There are always trade-offs.  The number one trade-off is usually cost.

I've read many reviews of mechanical locks having the exact same issue and being opened with a well-places rubber mallet strike.

The manufacturer will usually send a replacement lock for you to install or call a locksmith to do it.

I changed my electronic lock out for a Sargent & Greenleaf mechanical lock for my Costco Big Horn safe.  Installation was easy but required some precision at places.

My reason for the change was long term confidence in the lock working.  While I'd had zero problems with the electronic lock, I know trusting a battery-operated device in an emergency is often a bad idea.

If you're looking at EMP electronic locks with a key by-pass, you should do lots of research.  Mine tells me you're adding a layer of vulnerability to the lock, the opposite of why you got the lock in the first place.

Best advice I have is (1) change your combination every 5-6 months, particularly if someone else had access to it and is no longer there (ex, kid moved out, etc).  (2) Open and close the safe weekly.  This reinforces the numbers in your memory, ensures the dial is still working, and lets you practice "fast opens" if that's ever needed.

Beyond that, all mechanical devices are prone to failure.  Whether or not it happens to you is a "luck of the draw" issue.

When i worked for a bank, we had the safe serviced once a year.

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When i worked for a bank, we had the safe serviced once a year.

In the Air Force, for locks that protected safes, vaults and portable deployable computer facilities, we changed the combinations every 90 days or whenever someone with access to the combos left the unit.  We used to gripe when someone out-processed a few days after the 3-month combo change!

We had 16 safes in our office alone.  There were probably more than 150 in the building not counting the operations center that was open storage behind combo-protected doors.

The biggest problem was every safe had to have a unique combo and they could not be recorded except for the list kept in the commander's office -- just in case.

Yeah, having to memorize all those numbers and then do it again less than a week later was not fun at all!

We had a locksmith show up about every 3-6 months to drill out a safe that couldn't be opened with the combo.  I know those safes were very expensive and well-made.  If those can fail on a quasi-regular basis from daily use multiple times a day, I'm sure a home safe is at least as vulnerable to mechanical failure.

Had one lock guy tell me S & G was not a top brand for reliability.  Referred me to a newer company that touts extreme reliability over S & G

Locks look about the same, a patent may have run out.
http://www.bigredsafelocks.com/technical-support/

Interesting endurance video, with wheel failure as the culprit.

We had a locksmith show up about every 3-6 months to drill out a safe that couldn't be opened with the combo.  I know those safes were very expensive and well-made.  If those can fail on a quasi-regular basis from daily use multiple times a day, I'm sure a home safe is at least as vulnerable to mechanical failure.

Worked at a NAVAIR facility with a slew of those security safes.  Even had my own, with not much in it.
We had a rotating security check list at the end of the day where you went around to verify every safe was secured.  Never ran into a safe waiting for opening due to failure.  Couple dozen floor safes and a vault door.

Guess that experience had me thinking the darn things were infallible.   

Had one lock guy tell me S & G was not a top brand for reliability.  Referred me to a newer company that touts extreme reliability over S & G

Locks look about the same, a patent may have run out.
http://www.bigredsafelocks.com/technical-support/

Interesting endurance video, with wheel failure as the culprit.

You would hope a company that's all about security would be more careful about .... security: