I like having a bunch of info on the cam, so I usually measure the duration at 0.002", 0.004", 0.006", 0.008", 0.010", 0.020", 0.050", 0.100", 0.150", 0.200", 0.250", 0.300", and 0.050" above to max lift. For double check of centerline, I might add a few points around either side of max lift.
I just plug the numbers into a spread sheet and usually the centerline numbers are pretty close.
Here is what I had for the Comp 286 HR hydraulic roller cam:
Lobe Opening Lift: Crank Degrees Lobe Closing Lift: Crank Degrees CENTERLINE DURATION LIFT @ 1.6:1
0.002 42.0000 BTDC 0.002 260.0000 ATDC 109.00 302.0 0.0032
0.004 39.0000 BTDC 0.004 255.0000 ATDC 108.00 294.0 0.0064
0.006 36.0000 BTDC 0.006 252.0000 ATDC 108.00 288.0 0.0096
0.008 34.0000 BTDC 0.008 250.0000 ATDC 108.00 284.0 0.0128
0.010 32.0000 BTDC 0.010 248.0000 ATDC 108.00 280.0 0.0160
0.015 28.0000 BTDC 0.015 244.0000 ATDC 108.00 272.0 0.0240
0.020 25.0000 BTDC 0.020 241.0000 ATDC 108.00 266.0 0.0320
0.030 19.5000 BTDC 0.030 236.0000 ATDC 108.25 255.5 0.0480
0.040 15.0000 BTDC 0.040 231.0000 ATDC 108.00 246.0 0.0640
0.050 11.5000 BTDC 0.050 228.0000 ATDC 108.25 239.5 0.0800
0.100 3.0000 ATDC 0.100 213.0000 ATDC 108.00 216.0 0.1600
0.150 15.0000 ATDC 0.150 201.0000 ATDC 108.00 186.0 0.2400
0.200 27.0000 ATDC 0.200 189.0000 ATDC 108.00 162.0 0.3200
0.250 40.5000 ATDC 0.250 175.0000 ATDC 107.75 134.5 0.4000
0.300 58.0000 ATDC 0.300 158.0000 ATDC 108.00 100.0 0.4800
0.350 85.0000 ATDC 0.350 130.0000 ATDC 107.50 45.0 0.5600
0.360 98.0000 ATDC 0.360 119.0000 ATDC 108.50 21.0 0.5760