I've been measuring my X35 from day one. The very reason I paid a little extra to get the X35 over a cheaper end of line deal on an X30 was due to the new lamp/power supply. So far I think I made the right choice. I'm using a Tecpel 531 lux meter and I just do a simple centre of screen check using the 100% test pattern from my Lumagen.
When new I set it up just with some basic settings (6500K, standard colour space, custom gamma 2.3 all else at 0 apart from contrast to +5 superwhite to clip at 240 approx). It measured 93 Lux when set for 16:9 content (I have a 2.35:1 screen).
Then at 15 hours I ran a calibration and the output increased to a fraction over 100 Lux (15fL on my screen). This is therefore my base line.
I've checked many times over the last 3 months (paranoia anyone?
) and I've seen it vary between about 98-104 Lux. I did a full recalibration at 150 hours which still gave me 100 Lux on that occasion (it had been on for about 4 hours when I calibrated it). Since then I've just about hit 200 hours and it's just started to drop a little bit and my last reading after 4+ hours use was 93 Lux. So less than 10% drop from the initial calibration at 15 hours.
FWIW those readings are with the iris at -15 since this is still enough for my taste for 16:9 content. I open up to -8 for 2.35:1 content so that I hit 15fL. I'm at minimum zoom so at the lowest end in terms of light output, though of course for the same reason it means I get the best contrast (and a sharper image) than when zoomed.