I suppose it depends on the person, their level of training, and when that training was started.
As a high schooler on rifle team, we shot 40-50 rounds a day, 4 days a week, 9 months a year.
As an adult, when ammo was plentiful, the high end was 250 rounds pistol, 100 rounds rifle a week.........and now that ammo is not so plentiful, it's a box of 50 for pistol over the selected bouts and a rifle magazine of 20 a week.Admittedly, at the high end, I rarely got that since that was an afternoon at the range.
But in either case, my threshold to what I might degrade to might be higher than most.................in theory, since I've never had (and hopefully, never will have) to shoot at anyone, especially if they are shooting at me.
But.....the more frequent, the better.
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("So it took him a year to fall to his wounds but to tell you the truth, V. H., with the amount of ammo the anti terrorist squad put in him that day, he should not have been able to move at all."––"Jeremy" to Adderly about "The Jackel", (w,stte), "Adderly")