Here I am with another lamp question, this one is about LPS lamps. 

I can't find definite information about the life expectations when under or overdriving a LPS lamp (mostly interested in SOX variant).

Most of the posts here seem to imply that you need to be pretty close to the specified operating conditions (one place mentions ±10% of the specs) to have a normal lifetime out of a LPS lamp. Are LPS lamps like the European HID lamps, where you can dim them down to 50% with no adverse effect on lifetime (which some imply to even prolong their lifetime)?

I'll appreciate it if there are relevant papers on this topic referenced.