In general front projectors don't rack up hours nearly as quick. Their lamps tend to be much more comparitively expensive. It may be that, like 3 chip DLP, the main benefit of rear projection (lower cost) wasn't realized but would be much more reliable.
Or that front projectors racking up thousands of hours could well begin to see the same effect. Without knowing the number of optical blocks Sony has replaced and their internal memos / conclusions, it will likely remain speculation. For a long time, in this very thread, we were considering the Qualia 006 and XBR2. XBR2s look like they exploded big time, though they lasted longer than the A2000/A2020. IIRC there are now finally more than a few Q006...
Most consumer electronics is junk these days. Try to find a single non-high end display in the Display section without a serious issues. If it's not clouds, it's banding, if it's not banding, it's electronic failures. Sony to Samsung to Mitsu to Pioneer to Panasonic... it's all semi-disposable junk that will quite doubtfully be running in 20 years. Look at the Xbox 360 RROD and the PS3 YLOD. Stuff is made to as cheaply as possible... I think SXRD is great tech and could be viable. I'm still a big fan of rear projection, in fact... it's just Sony didn't make the design to be upgradable or easy to maintain (look at how deep the fans are and where dust accumulates). I would love a modular rear projection set designed with the long term in mind... Rear projection with replaceable lamps is well suited to that, but the corners can't be cut. A modular, easily accessible well engineered design would be great: "upgrade your video processing from WEGA to Bravia 2? Undo the thumbscrews and Remove panel A, Change out this card." "Want to upgrade your HDMI board, change out that card." etc etc. But it's not in anyone's design paradigm right now.