When revolvers were the "standard" LE handgun, there were many, many S&W M10's and M15's at LEO academies that were pretty well documented as to round count. Typically with light wadcutter and / or standard pressure lead loads, these guns with an occasional cylinder stop or hand replacement and some yoke peening, etc. would easily pass 500,000 rounds. ("X" number of rounds per gun per class x "X" number of classes per year x "X" number of years, etc) +P loads with lead bullets increased wear significantly as did jacketed bullets.
9mm autos at today's academies have also done well, although the number of years they last is down due to a great deal more shooting by recruits, including many rounds on reactive steel target systems, the use of factory, jacketed / plated bullets and the much higher chamber pressures of 9mm loads in general. Many of these guns will see 10 or more classes a year and fire 600-800 rounds or more per class...60,000 to 80,000 rounds per year. It does not take long to reach a 500,000 round count at that rate. The Berettas hold up as well as any others and better than many BTW.
My guess is that we will not see the various .40 caliber pistols now being used at some academies hold up nearly as well as the 9mm's, and I will not be surprised to see them expire at less than 250,000rd.
Few handguns ever see anywhere near this number of rounds simply because, even if shooters had the money to buy the ammo, they do not have the time or range access to shoot that much...remember, the guns above were used by many different shooters, sometimes with both day and night classes going at the same time. The IPSC guys who shoot .45's and "retire" a gun at 100,000 rounds do so more out of desire to keep up with newer trends and rules than because of any real need to stop using the gun...most just need a tune up at that point, and often even that is only to keep up serious accuracy...the guns function fine. Occasionally you will see a dust-cover crack on the side if a frame, but the gun can do just fine even if you cut the dust cover completely off! The higher pressure rounds like .38 Super or .40 are a different matter of course.
FWIW, the handgun with the generally recognized LEO acadeny reputation as "toughest of them all" was the Ruger Security/Speed Six...crappy action, ugly gun, but tough as woodpecker lips!