I received an offer from McK.
PEI should be about 2/3/4 mins. Any longer and you're giving too much away and will probably send them to sleep with details.
You generally only have 12-15 mins total for the PEI so you need to leave enough time for them to ask follow up questions. What i would suggest is to cut down your story and then drop little teasers in the original story so that you can help predict what follow up questions you'll be asked.
For example: If you are talking about conflict and how you managed a difficult team member i would say..."i took a number of steps that helped me resolve this issue, for example bargaining with them to offer insight to leave their shift early." Of course, the interviewer is then going to say...what other steps did you take?
This will make your story sharper. Dont leave out too much but also dont give them EVERYTHING. If you provide every single detail, you're rolling the dice and will have to make up answers that come your way. Play the game, dont let it play you!