Those who have regeared, how often are you changing gear oil?

I have Nitro 4.88s and use Lucas 85-140 dino oil. Just curious how often everyone is changing out their gear oil.

ECGS posted this on their website:

• Temp Reference Chart – oil change frequency
o 170 Deg - 100,000 Miles
o 200 Deg - 50,000 Miles
o 220 Deg - 25,000 Miles
o 240 Deg - 12,000 Miles
o 260 Deg - 5,000 Miles
o 260-300 Deg – 500-1000 Miles until Temp is controlled

• Differential Temp Guide
o 250-275 Degrees is Normal for new differentials breaking in, do not Tow or take long road trips for first 500 miles as this builds additional heat. 300 degrees is to hot and diff should be allowed to cool.
o Normal operating Temp for a differential adequate for vehicle in stock applications 170-220 degrees
o Normal operating Temp - Large tires, Undersized Differentials, Towing 200-250 Degrees.

So based on this I'm thinking somewhere between 10-15,000 miles. Does that sound about right? Not aware of any way to actually monitor diff temps, but I do live in the desert where it gets 120+ in the summer.