S.M.A.R.T. lifetime hours resetting to zero
How you can see from SMART attribute 9, your SSD lifetime is correcly reported in the full report:
9 Power_On_Hours 0x0032 093 093 000 Old_age Always - 33168
On the other hand, the LifeTime(hours) value reported for self/short/long tests seems to wrap at ~49 days, similar to how SMART error reporting works. From smartctl man page:
This is displayed in the form Dd+HH:MM:SS.msec where D is the number of days, HH is hours, MM is minutes, SS is seconds and msec is milliseconds. [Note: this time stamp wraps after 2^32 milliseconds, or 49 days 17 hours 2 minutes and 47.296 seconds.]
This is one of the field where the once consumer related SMART heritage shows, as it is (was?) uncommon for a desktop to have >49 days uptime.
Most disks with SMART would use 16 bits to store this value, giving 65,535 hours before reset.
Yours appears to wrap after 1152 hours which is not a convenient power of 2 and is quite odd.
Here's a disk that has just completed its second time around that clock, with 139,895 hours of power-on time, but the SMART self tests wrap at 65,535 hours.
SMART Self-test log structure revision number 1
Num Test_Description Status Remaining LifeTime(hours) LBA_of
# 1 Short offline Completed without error 00% 8823 -
# 2 Short offline Completed without error 00% 65041 -
# 3 Short offline Completed without error 00% 63134 -
# 4 Short offline Completed without error 00% 43108 -
# 5 Short offline Completed without error 00% 42235 -
# 6 Short offline Completed without error 00% 30613 -
# 7 Short offline Completed without error 00% 11535 -
# 8 Short offline Completed without error 00% 5934 -
# 9 Short offline Completed without error 00% 2667 -
#10 Short offline Completed without error 00% 2666 -
#11 Short offline Completed without error 00% 54241 -
#12 Short offline Completed without error 00% 47079 -
#13 Short offline Completed without error 00% 43109 -
#14 Short offline Completed without error 00% 43071 ... etc
Yes this disk has about 16 years of active power-on time.
9 Power_On_Hours 0x0032 001 001 000 Old_age Always 139895
I'd suspect your Apple SSD has some extra firmware fudges going on allowing it to report odd times. It would be interesting to check the SMART values on a non-apple disk, attached by USB perhaps? Or to check an apple firmware disk in a non-apple system.