I'm currently a Manager at a Big4 firm, thinking of moving to Senior Manager in about a year-18 months. I'm considering moving to Accenture (I'm up for a second interview for M2 grade) but I've heard horror stories about 100 hours a week the back of beyond. A lot of forums seem to be very bitter so a balanced view would be great.

That is probably an exaggeration, 80 hour weeks are more typical, but you could well end up well away from home. Expect to gain around one stone in your first 3 months due to hotel food and a lack of time for exercise.

If you stay at any firm long enough you'll probably be on a death march project eventually, but in general tales of constant 80-100 hr weeks are a total exaggeration. That's not to say people have never worked those kind of hours (which i and probbaly many have) or that people have never done crazy 24/36/48 hours straight (which i know off some years ago), but constant (i.e. more than a week here or there) is just not really feasible, certainly in this working environment.Will vary dramatically by role, industry, level, client etc, so it is hard to generalise. More likley 40-50 hours a week with spikes to 60/70 hrs a week during specific phases of a project.There is of course a risk that if you are out of town on a project you end up working more hours because you dont have anything else to do, but that is then up to you to make sure you have something outside of work to do.

I suspect it all evens out in the long run... i.e. a 9 to 5 industry job (40hrs/wk) also does not normally have two weeks of bench, plus 25-30 days holiday per year.I would say my overall run rate is somewhere between 50-60hrs / wk totting up overtime, bench, holidays, etc.However I have been on those fabled 3 month death march projects where your phone is pretty much on the charger 24/7, 8 am 2hr daily "taskforce" meetings, reams of excel / ppt, pot noodles at a holiday inn express while finishing up emails at 1am... been there, done that, got the t-shirt. It happens, and as you become more senior it happens more often.

You should be more worried about Accenture's demonstrated inability to assimilate experienced hires. You will probably be recruited below your actual level, given tasks you got bored of three years ago and then suffer when compared to your peers because of your lack of a network.At that level you will see/take part in many death marches. On the bright side, you will learn how the definition of success can be quite subjective.

I too have seen SEs able to 'spin' failure as success. I think it is a key competence at that level. However, clients aren't completely stupid and everyone knows that a delivery must score reasonably well on at least 2 of the 3 project management KPIs.