About 1/2 hour for DD1. That is me saying 'Okay, time to get ready for bed' at 6pm, brushing teeth, chasing her for 10 mins to get pyjamas on, reading 2 stories and kissing goodnight. On bath nights it takes an extra 15 min and on nights she is being 'difficult' it can take an hour. DD2 i do the teeth, pyjamas and bath at the same time and then about 10 mins after DD1 has gone to bed (and is asleep) i give her a bottle, read a story and put her to bed - that takes about 10 mins.
My night routine with my youngest used to take about 3-4 hours but her sleeping improved dramatically in the last month so now she is much easier and quicker to settle to sleep. (thank goodness as i wasn't coping very well).
ETA: My girls are 3.5 and 21 months.