Is it unusual if you are a M3 who has been rated 5/5 this year and for the past two years but was not considered for a promotion to SM?

No, not unusual in PI anyway. Typical track is 4 years at M

OP - what practice ? In PI there are a lot of very experienced Managers. There are only a limited slots for new SM. In scenarios like you mentioned, it's better for the firm to promote higher performing, but more experienced managers (M4/M5), than to promote high performing, but less experienced managers (M3 and Below). These is a lot of lateral hiring at the M level, and it is possible that many of them were SM material when they were hired.

Agree most take 4 yrs at mgr. some but very few do it in less.

Not unusual. I was in similar situation for a few years. Aside from doing great work you have to perform "at the next level" for at least a year in order to get promoted. Depending on project size you may not have a chance to do this.

I'm in this exact situation have consistently been a top performing manager, currently an M3 and the messaging has been you've had a fantastic year, but there are a lot of M4/M5s and it's going to be really tough to "jump" ahead of the line, which is bullshit because I am performing at the SM level and there are a bunch of relatively worthless SMs in my practice. In PI if you're curious. So unless there's some huge raise (which I'm doubting) not sure that I plan to wait until next year.

How long is path to partner at EY? 5 years at manager is insane.

Yes, I'm in PI as well. So @Manager 2, are you thinking industry or another consulting firm?

I've only done consulting in my career so likely consulting, but if something interesting came along in industry I'd think about it.

@Deloitte 1: for better or worse, I think EY is less up or out than Deloitte. That provides a bit more job security, but can also slow down career growth because it's acceptable to be at a rank for longer duration.