How long do thunderstorms on Venus last?
Independent observation led to the conclusion that lightning is prevalent on Venus. Electromagnetic signals detected by the 4 Venera landers explained the main cause of lightning on Venus. Venera 9 spectrometer detected a lightning stroke. The Pioneer plasma wave instrument detected waves which explained lightning might be at low altitude. VLF observation suggested that lightning is a intra-cloud  phenomenon which is more common in the afternoon and evening time and the occurrence rate is more as compared to Earth. Venera 11, 12, 13 14 were equipped to detected magnetic signature(acoustic data were also obtained from V11 and V12).
Lightning on Venus occur from strong convective cumulus cloud and occasionally from dust storms and volcanic clouds. The clouds may vary in altitude from few km to 30 km . Lightning on Venus occur due to two distinct forms: cloud-to-ground discharge and intra-cloud discharge. Such discharge occur when electric field exceeds from 106 V/m in wet air to 3 $\times$ 106 V/m in dry air. Cloud to ground discharge carry current from 200-300 A which increase every 50-100m, travelling at a velocity of 1.5 $\times$ 106 m/s which followed with a return stroke with velocity 0.6 $\times$ 108 m/s carrying 10-20 kA which decays in about 20-50 us. There are 3 or more stroke in one flash separated by 40 ms and lasts 0.2 s.
Discharges within clouds are 2 to 4 times more frequent than that of cloud-to-ground discharge and carry currents upto 4kA but they generate less energy(4.5 $\times$ 108 J in cloud-to-ground discharge). Number of discharges on Venus is more than that of Earth. Over 7000 discharges occurs on Venus per day  You can check the details and observation in ref.1 and ref.3

Fig. 1 Venusian atmosphere where lightning is most likely to occur

Fig.2 Magnetic field due to intra-cloud discharge (altitude 50 km)
References

Venus lightning by Russell, C. T., Space Science Reviews, vol. 55, Jan-Feb 1991, p. 317-356. (link and the author's paper here)
Russell, C.T. et.al. (2011). Venus lightning: Comparison with terrestrial lightning. Planetary and Space Science - PLANET SPACE SCI. 59. 965-973. 10.1016/j.pss.2010.02.010.
Lorenz, R.D. Lightning detection on Venus: a critical review. Prog Earth Planet Sci 5, 34 (2018). https://doi.org/10.1186/s40645-018-0181-x