I clean my guns maybe once a year. In between then I may fire off perhaps 5-10 high power rifle rounds, perhaps 50 pistol rounds just to make sure I am still on target, or to shoot some nuisance animal around my place.
When I finally do clean my guns I thing the AR takes the longest because you should get all that gunky stuff out of the locking lugs. That would take perhaps an hour.
A bolt action rifle, perhaps an hour or less.
A revolver, perhaps 20-40 minutes - depending on detail, removing all carbon from the front of the cylinder, etc.
A semi-auto pistol, perhaps 40 to 60 minutes, again, depending on amount of detail.
If I just want the gun clean and lubed, I can usually do that easily within 20 minutes. However, if I detail it with Q-Tips, tooth brushes, plenty of soaking parts in Hoppes 9 and good thorough lubrication and wiping it down, an hour would go by pretty quickly.
Fornately, my house is always very dry, so the guns seldom get rusty.