I believe that those irrigation companies estimate the maximum wire length between station and solenoid according to estimated resistance of the wire, and the estimated inductance of the wire. These will depend on the particular sort of wire/cable being used. One way to possibly figure out a maximum length is to take whatever system you have at the moment, and use an AC voltage measuring device (eg, multimeter) to measure the voltage at the solenoid when the controller is supplying AC voltage to it. The controller output will be about 24 V AC (RMS). But the voltage across the solenoid is expected to be smaller, due to resistance and reactance of the long cable. If you know roughly the length of the existing cable, then you can take the difference (call it "DIFF") between 24Volt AC (RMS) and the measured RMS voltage across the solenoid. This will be the estimated voltage drop for that length of cable you currently have. Then, the voltage drop per unit length will be equal to DIFF/existing_cable_length, ie. DIFF divided by existing cable length. Call the result of this something like dpu (drop per unit length). So, this should let you calculate (estimate) the voltage drop for a particular length wire/cable. As long as the drop is not more than say '4 Volt', then it should be ok. This means, the AC RMS voltage across the solenoid terminals themselves, should be at least 20V AC. The voltage drop calculation will be dpu times length_of_new_cable.

That's what I do now, but it's a PITA. I'm forever adjusting the run times, turning it off, turning it on. My controller at the old house at least allowed me to specify a number of rain delay days and to make percentage seasonal adjustments. The current one requires a step ladder, a flashlight and a lot of button tapping for the same activity. By the time it rains again, the battery has died on the rain sensor. My real problem, though, is that when I travel in the spring and fall. rain and Santa Anas always seem to arrive while I'm gone!

Alas, no Blossom app in Windows Store, plus product appears to need substantial "maturation." First couple of Amazon reviews that pop up are pretty poor...

UPDATE ON RACHIO. CYBER-RAIN COMPANY APPARENTLY CAME BACK TO LIFE... BUT I DISCARDED THAT 4 YEAR OLD IRRIGATION CONTROLLER ANYWAY. I HAVE HAD THE RACHIO FOR 6 WEKS NOW. IT IS UNBELIEVABLY GOOD AS A PRODUCT. INSTALLATION A BREEZE. SOFTWARE FANTASTIC. CALLED SUPPORT 2 TIMES JUST TO CONFIRM MY UNDERSTANDING OF BEST WAY TO ACCOMPLISH WHAT I WANTED. MORE POWERFUL THAN I THOUGHT. CUSTOMER SERVICE FANTASTIC. IF YOU NEED A NEW OR REPLACEMENT IRRIGATION CONTROLLER. READ THE HUNDREDS OF REVIEWS ON AMAZON. YOU CAN NOT GO WRONG. HIGHLY RECOMMEND EVEN MORE, AFTER RUNNING 6 WEEKS.