Count me among in the screwed by flickering issues crowd.
I've had my VPL-HW55ES for over a year now, and used it heavily every day. Sometimes often 12+ hours a day. I ran into flickering within the first 3 months of use.
The only bulb that never flickered was the very first bulb, the one that came with the projector. It was branded LMP-H202 on the bottom, and the sticker on the phillips bulb mentioned the wattage and temperature rating.
My first replacement bulb was the 'free bulb with coupon' from Sony, an official boxed and branded LMP-H202 with filter and documentation. I wanted to burn in the bulb right away, so I swapped to it after the OG bulb had about 500 hours. This new bulb started flickering within 500 hours. I had already done the '100 hours on High' conditioning with this bulb, it didn't make a difference. This bulb did not have 'LMP-H202' or whatever or sony branding on the cartridge. The bulb had a sticker with just a serial number on it. I would later discover this is identical to 3rd-party cartridges and bulbs.
I swapped back to the original bulb and left the 'free bulb' unused until the original bulb reached about 2000 hours and was starting to be noticeably dimmer (the expected wear state). I had forgotten to take advantage of the official sony bulb's warranty, so I bought a 3rd-party bulb which used the same Phillips bulb. Having examined the cartridge, it's obviously nothing special and a mock-off would perform identically, so the real potentially sensitive item is the bulb itself.
The third party bulb also started flickering within 500 hours. I RMAd this bulb, and switched back to the 'sony free bulb'... this bulb would flicker after using the projector for 10+ hours, so I had to baby it, but continued to use it until about 2000 hours at which point it would flicker immediately upon putting it in the projector.
I switched to the RMA'd (new) 3rd-party bulb... this bulb also started flickering within 500 hours.
I've now sent my projector in for repair and so far they've been unable to reproduce any issue and want to charge me over $600 for a cleaning and a new bulb.
Here's some facts:
-- 24hz makes flickering more apparent, but it's still present at 60hz just less noticeable... input signal frequency likely couples somehow to the frequency of the bulb's input power (possibly the projector uses the HDMI signal's clock as a reference and then uses that when generating the PWM power to the bulb)
-- switching between high mode and low mode serves to change the current being driven to the bulb which seems to temporarily alleviate the issues sometimes, but when the issue is bad enough it makes no difference
-- after 10+ hours of use the flickering is significantly more likely to occur, and sometimes won't go away until the PJ is turned off for 1+ hours to cool down
-- using high fan mode seems to increase the time until the flicker occurs
-- new bulbs seem to not show the issue for a while, thus the issue appears to be extremely aggressive permanent bulb degradation (likely anode\cathode wear)
This leads me to believe that the projector is not engineered correctly to deliver consistent power to the bulb under all common operating conditions. e.g. in a <80 degrees Fahrenheit room, with high fan speed on, after 10+ hours the circuitry delivering the power begins to fall out of spec. I used to do board level repair for laptops, and the high voltage inverter boards that power the CCFL backlight bulbs is very similar to how projector bulb circuitry works... if these have issues with power filtering, regulation, or delivery (noisy power, ringing transformers, etc.) you could end up with flickering.
I think these PJs are incapable of operating to spec and are aggressively destroying bulbs due to dirty or unregulated power (after the DC conversion), and insufficient cooling to the device.
Bulbs should not flicker as they age if they've been powered adequately over their lifetime. They should begin to dim, lose contrast, and shift color, and get increasingly worse, but flicker is not a guaranteed sign of bulb death. (In fact, google 'laptop backlight flicker' and tell me how many cases you find where replacing the bulb fixed it instead of replacing the inverter... it's a power delivery issue!!)