Short generator use

The 30 minute run time is not only too short to reach operating temp, but to keep it there long enough to drive out any condensation (water) in the oil.

Also remember to apply a load to the generator when exercising it.

The main problem with short generator runs is the condensation in the exhaust and in the oil.
If you don't heat up the oil enough, moisture will not evaporate, and it will cause internal damage over a long period of time. Usually 10 minutes works fine to heat up the motor enough if it's aluminum.

Exhaust however, takes longer, especially if there isn't a heavy load on the motor. Hold your hand to the exhaust. If it doesn't feel really hot or if it leaves your hand damp, then it should be run a bit longer. Moisture condensed in the muffler will rot it out quick, as in a year or two.

It's best to let it warm up for a minute or so before applying a heavy load, but beyond that short runs aren't particularly bad. Most of the wear (for any gas engine) happens during and soon after a cold start rather than during continuing operation once up to temperature. If you do a lot of short generator runs, it would be a reasonable idea to change the oil in it more frequently than otherwise.

(Not intending to open too big of a can of worms, but there are several good ways to make coffee that don't require using the generator....)

The 30 mins/mo. is a service interval recommendation. The mfg knows that a month interval between operating is going to keep the machine operating better. There is no problem operating the generator for shorter durations.

Is this by any chance, an Onan generator? Cummins/Onan is real specific about schedule of operating intervals.

A good way of thinking about generator maintenance and service is to mentally multiply usage by 100's and compare that to vehicle service. For example: A generator operated for 100 hrs would need the same typical services for a vehicle operated for 10,000 miles. Most folks are more conversant with vehicle maintenance than small engine service.

No issues for us when running generator for short durations, most often occurs in the morning during breakfast when getting ready for the day. We do lots of RVing off the power grid and use our genny often for short durations although we will let it run at least 10 minutes or so.

A gasoline engine is going to be well lubricated within a minute, hot within 5 minutes, and really hot within 10 minutes. No problem with 10 minute runs.

The purpose of exercising is to eliminate moisture, insure the generator is properly lubricated and to mitigate carburetor issues. Many run the generator 1-2 hour rather than 30 minutes. Using generator for shorter than 30 minutes is no big deal - that's how I make coffee in the morning.

If you use it somewhat regularly then shorter use is not an issue, there is a bit of unusual wear in the first minute or so - so keep that in the back of your mind if using it too often for short uses.
Their idea is to get the oil spread around inside, on the cylinder walls and to a lesser degree in the bearings, and move the stalest gas (esp., but not limited to, ones with carburetors)