As mentioned an another board where you posted this questino, it really depends on what agency and even what position in an agency. An OIG may do very little BUT paperwork... some do not even carry guns!
I can speak to the USMS very well. Some 1811s spend a lot of time in court, tranpsort and other prisoner-related duties. Others are more fortunate, and are assigned to full-time fugitive investigations. Most of our investigations are NOT prosecutorial, meaning we need to document a lot less. I am part on a fugitive task force and I spend about half my time each day doing reports, etc. Most spend less than this, but I am in charge of this crew and and extra reports to write each day, review others' reports and assign/manage cases. Most other Agency's 1811s would be hard-pressed to have such a good a$$-kicking to paperwork ratio!
I know some buddies of mine in the FBI and ATF spend a lot more time at their desks. Then again, so do a lot of my colleagues in the main USMS office here. 
Bottom line is that it varies!
We bring evil things to evil people, kicking in a door near you!
."In theory, there is no difference between theory and practice. But,
in practice, there is."
- Jan L.A. van de Snepscheut
"The difference between 'involvement' and 'commitment' is like
an eggs-and-ham breakfast: the chicken was 'involved' - the pig
was'committed'."
-unknown
Working on a PhD in CQB one doorway at a time.
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