If you live long enough, you start noticing that soldiers, police officers and your bosses get younger every year.

In the first letter in today's Monday Morning Quarterback, a longtime fed says that President Reagan has turned midlevel government into a training academy for young, inexperienced political appointees.

Another letter writer, a federal retiree, says he and his civil service wife can't keep up with the Joneses even though they happen to be schoolteachers.

Here are their comments, plus some other letters from people about the way things are working (or not working) in the government:

*"President Kennedy, rich as he was, is remembered for having established the Peace Corps. President Reagan, as mature as he is, should be remembered for having established the Kiddie Korps. Using government as the training ground for How to Manage After College, the president has flooded the sub-cabinet ranks with people inexperienced in swimming in some pretty deep water.

"Rather than hitting the career civil service over the head, the president should include us in his Thankgiving prayers for continuing to take care of his many 'children.' " Washington Civil Servant

*"As a federal employe, my wife will get no increase in her salary this Janaury. As a federal retiree, my cost of living adjustment will be about $340 for 1986.

"However, some local public schoolteachers got a 10 percent raise for the current school year. Assuming a salary of $25,000 for the teachers, two of them in the neighborhood where we used to live got an increase of $5,000 for the school year.

" . . . No wonder that these two public employees can fly to California for two weeks during their three-month summer vacation while my wife and I have to think carefully about an off-season weekend trip to the beach.

"I wonder how much of an increase in salary and other benefits all the people who work in private industry -- under a federal government sole-source cost-plus contract -- will get while we are spending around $340 next year?" R.A., Manassas

*"Attached is a recent clipping from Chemical Week Magazine telling of an early-retirement offering available to Monsanto Chemical Corp. workers who are age 50 or over that includes a one-time payment ranging from 50 to 140 percent of salary . Within the last year, the DuPont Company sponsored a similar event.

" . . . Take this into account next time you publish your time-worn canards on 'how easy' the bureaucrats have it." R.C.B.

*"Mike, I realize you have to make a buck . . . writing a civil service column but really . . . sometimes you sound like a cheerleader with the team, naturally, your precious feds and retirees.

"Last week, as an example, you wrote that federal retirees will be getting a 3.1 percent cost-of-living raise in January. The headline in your column said 'Retirees COLA Shrinks.' You pointed out, correctly, that because of the 'decline in the rate of inflation and changes in government pension policies' this would be the lowest retiree raise in more than 20 years.

"Though you had the facts, you missed the point! Of course this is the lowest raise in years! This administration has brought inflation down and Congress has reversed policies that gave federal retirees inflation protection-plus that is unknown to private sector retirees. Your civil service team isn't getting hurt, just what it deserves!" H.B., Arlington