burn in - how important?

Over the years following Agon forums I have read many postings about burn in and been fairly sceptical, as many items I have bought over the years have changed SQ very little or at all, after years of use. Recently I replaced my Rogue Stereo 90 with a used EAR 534 power amp. Out of the box it looked brand new, all nice and shiny. I plugged it into my also fairly recently acquired Aesthetix preamp and was horrified by the thin sound, little or no soundstage and was relieved I hadn't yet sold the Rogue. Now I knew why it had been up for sale or did I. Maybe I was too lazy to plug in the Rogue again but I left the EAR in place and after about 30 hours I noticed a difference, more depth, wider soundstage, Now after about 100 hours - WOW huge soundstage, both depth and width. great tight bass, shimmering highs. Now I know why Tim De Paravicini was regarded as a genius and sorry for the seller who probably had not given the unit a chance to burn in properly. I decided to biwire it into my ML Vantage speakers and cut out the second Acurus a250 amp which I was using in biamped format. There was hardly any difference, maybe quieter and more detailed overall. Who would have thought an EL 34 based 55wpm channel Class A amp could drive a pair of electrostatic hybrid speakers rated at 4ohms. OK no longer a sceptic about burn in but a firm believer. What has been your experience?