'(although, I have to say, the 4 day a week PSL to partner thing is not a "likely" career track IMO)'
lol, Anchovy is right. That PSL was not only good, she was also in the right place at the right time and thedog's whatsits to boot (to borrow Undercover's terminology) and even then took many years to get there.
Rosie, it is hard enough to get partnership fulltime, and even harder parttime. Are you at the seniority where the senior partners in your team start telling you where you stand? Can you identify a credible champion amongst the partners in your department, who is prepared to push you through? What do you reckon your business and personal case is?
There is all the extra profile building (seminars), client development, etc on top of billings, that you have to do in the run up to partnership.
All it means is that if you must WANT partnership (hard in these times to just fall into it), and then actively pursue it. If you are prepared for that commitment, then you can plan when you are ready for the push.
Is your firm up or out or can you 'coast' (hate that word) on 4 days until you are ready to gear up for partnership when your children are slightly older.
Anchovy, do you think it is possible to do the push on 4 days, based on strategic socialising and profile building. In your case, you had children post-partnership, but Rosie has to run the race pre-partnership.