I only replace the rotors when they get down to or below spec thickness, which is printed on the edge of the rotor. I bought a digital calipers so I can measure them. The other indication I use to change the rotors is if they get warped at all. You can tell this by the pulsating of the brake petal.

I think the responses you get to this question will vary, but there is a definite bias on this forum toward frugality so I would venture to say that a majority of the members do not change them with each change of the pads.

When I did replace my rotors, I purchased a good quality brand. I stay away from cheap metal that will likely warp sooner. They will be a few dollars more but of way better quality.

__________________
85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60