I got a new Owon SDS7102 oscilloscope and I'm using the included oscilloscope probes with it.
The manual says that the proper calibration procedure is to let the oscilloscope work at constant outside temperature for 25 minutes, do the oscilloscope's internal calibration routine and then set the probe capacitance using the included tool. The manual also says that the correct capacitance should be checked often and corrected if necessary. What the manual didn't mention is how often
I expect that checking probes before each important measurement would be needed, but I'm looking for some "rule of thumb" for general use. From my current experience, several hours are enough to see small loss of sharpness of the calibration signal.