Former Artilleryman,
M777 could be good for 4000 rounds. Could burn out in 1000 rounds. Depends on what charge, rate of fire and projectile weight. Charlie Battery 1st and the 37th Field Artillery ( my old unit) was the first unit to field the M777A2 in the US Army in early 2008.
We fired over 1400 rounds in a week for table 7-8 training. Most was Green bag(charge weight) about 40 RAP rounds and probably 100 Red bag charges. The guns were sent in for service after. They were 1/4 through there service life after that we were told.
And I highly doubt they "trained" them competently. 13B training is like 5 weeks, 13D training is 7 weeks and a day. You just know enough to think you know what your doing. The real training and experience comes from being on the line. Sure they can pull the string... But unless they are former Artillery men. They are gonna be sub par.