Laser life is something I've been looking at over the last few years. It seems the best quality machines lasers last around 4 years with average use. after three years they become weak and picky about the disc's used. The cheap machines only just last the warranty before getting picky and often die at around two years. Obviously this isn't very scientific, but never the less a careful long term observation from repairing DVD players etc. Computer drives are about the same, the better quality drives last longer.
Upping the current to the laser will sometimes help, but usually spell the death of an old laser.
Some of the better machines (DVD recorder stand alone's and puter burners) are worth repairing if the parts are available, but unfortunately not viable in a workshop as the time involved to fit a re set up the laser units is more expensive than a new machine!
Some of them are damn near impossible to set up again, because the manufacturers wont release the parameters or manuals.
Overall, expect to replace a decent quality machine around every three years and the cheap ones, well that's down to luck.
Yup the solid state lasers have a very short life span, too short if you ask me. I hope the new Blueray ones are better.