Apparatus, comprising: a catheter configured to be inserted into an organ of a human body; a first electrode and a second electrode deployed on the catheter, the electrodes being configured to transfer radiofrequency, RF, ablation energy to tissue of the organ; a first temperature sensor coupled to measure a first temperature of the first electrode; a second temperature sensor coupled to measure a second temperature of the second electrode; a power supply configured to provide the RF ablation energy; a switch connected to the power supply and configured to direct the RF ablation energy to one of the first and second electrodes (33A, 33B); and a processor configured, while the power supply is providing the RF ablation energy via the switch to the first electrode, to monitor a first time for ablation via the first electrode and a second time for ablation via the second electrode, and, responsively to the monitored times, to toggle the switch so as direct the RF ablation energy to one of the first and second electrodes (33A, 33B), wherein the processor is configured, upon sensing that the first time for ablation equals or exceeds a preset first time for ablation for the first electrode while the second time for ablation is less than a preset second time for ablation for the second electrode, to toggle the switch so as to direct the RF ablation energy to the second electrode; and wherein the processor is further configured to monitor the first and second temperatures and, responsively to the monitored temperatures, to toggle the switch so as direct the RF ablation energy to one of the first and second electrodes (33A, 33B), wherein the processor is configured, upon sensing that the first time for ablation does not equal or exceed a preset first time for ablation for the first electrode while the second time for ablation is less than a preset second time for ablation for the second electrode, and upon sensing that the first temperature exceeds a predefined ablation temperature threshold while the second temperature does not exceed the ablation temperature threshold, to toggle the switch so as to direct the RF ablation energy to the second electrode. a catheter configured to be inserted into an organ of a human body; a first electrode and a second electrode deployed on the catheter, the electrodes being configured to transfer radiofrequency, RF, ablation energy to tissue of the organ; a first temperature sensor coupled to measure a first temperature of the first electrode; a second temperature sensor coupled to measure a second temperature of the second electrode; a power supply configured to provide the RF ablation energy; a switch connected to the power supply and configured to direct the RF ablation energy to one of the first and second electrodes (33A, 33B); and a processor configured, while the power supply is providing the RF ablation energy via the switch to the first electrode, to monitor a first time for ablation via the first electrode and a second time for ablation via the second electrode, and, responsively to the monitored times, to toggle the switch so as direct the RF ablation energy to one of the first and second electrodes (33A, 33B), wherein the processor is configured, upon sensing that the first time for ablation equals or exceeds a preset first time for ablation for the first electrode while the second time for ablation is less than a preset second time for ablation for the second electrode, to toggle the switch so as to direct the RF ablation energy to the second electrode; and wherein the processor is further configured to monitor the first and second temperatures and, responsively to the monitored temperatures, to toggle the switch so as direct the RF ablation energy to one of the first and second electrodes (33A, 33B), wherein the processor is configured, upon sensing that the first time for ablation does not equal or exceed a preset first time for ablation for the first electrode while the second time for ablation is less than a preset second time for ablation for the second electrode, and upon sensing that the first temperature exceeds a predefined ablation temperature threshold while the second temperature does not exceed the ablation temperature threshold, to toggle the switch so as to direct the RF ablation energy to the second electrode.