Good honest review. I'll paste in below the reply I gave someone who was asking about the SR125i. It discusses the run-in or burn-in you talk about. I go on to talk about the SR225i. I edited this in from another post someone was asking about the 125/225 comparison.
Grados straight out the box are most definitely harsh. I have never heard anything like it. They sound flat, undetailed, coarse, and with no musicality whatsoever. A bit like an old qualityless portable tranny radio, with a vague stereo soundstage.
However let them run in and all aspects of change take place. I say they need three solid days to settle. That's seventy-two hours. (Leave them on sound source over-night.) They will refine after that but three days to me is when they really feel their legs. During the first three days the sound softens, becomes accurate, and the soundstage gets its spacing worked out.
The first couple of hours changes are subtle but tonality starts becoming apparent. After that and as time goes by the timbre of the music improves. Until eventually you are in an emotional relationship with the headphones, after somewhere between three days and a week's time.
Personally, I recently bought SR125i which have an exceptional quality, that went faulty after about three weeks. Amazon had no more so I returned them. I ended up with SR225i. The 125i have a slightly more floaty sound, with lots of details, and luscious timbres. The 225's are the clearer "repristinate". Slightly like someone has removed a thin sheet of felt from between you and the music. They have an awesome depth of spatial. I mean sounds come from so far around, not in the head, if your sound source is so geared. I.E. SR225i are less floaty, just as soft, solid, representative, and more agile and dynamic.
The main complaint of the 225 up to 500 is physical comfort. I listen to them for hours often leaving them on after the music stops. I discovered the following specific to the L-cushion pads that nearly everyone complains about. First time I put them I had them on minimum length pulled out on the earphone legs. They fit perfectly. For some reason I slid the earphones down the bracket legs a little. (I.E. Making the headphones longer from top to bottom, and the earphone lower down my ear.) After a while I got uncomfortable and moved them more. Uncomfortable moved them more. Pain and ready to stop wearing them at this point. Then I remembered I liked them at first for comfort and pushed the earphones back up the legs. Perfect! You just have to find your right place.