There is an recommendation in the original Rishikesh sequence which has the pranayama after asana and shavausan and before meditation. I have only recently learned of it. I believe one of the foremost asana teachers does it in private and I learned of it from him. I will begin soon once my pranayam practice regulates. In daily practice we may do pranayam for 15-30 minutes each of kapalabhati and anuloma. In intensive courses we may do 4 hours or hundreds of rounds. A friend just returned from a one week intensive and they did one hundred rounds and one hundred retentions each lasting hours each day.
Now in practice for a yogi who has studied pranayam for some while under guidance Sivananda reccomended at the least 15 minutes of Anuloma and kapalabhati. Ideally after asana and shavasan and before meditation.
In class we do something like 3 rounds of kapalabhati something like EDIT: 45-60-75 interspersed with 3 retentions of the same 45-60-75. I do not count while retaining I usually meditate or do japa so we may go two minutes in advanced class. the focus is easier when desire is gone.
I have not done advanced pranayama though I am told that I am naturally doing some of it but should have instruction. Janaki of CZ has had some advanced pranayama techniques at the ashram and I know they are very powerful and not to be done without guidance.
The counts vary but they always follow a ratio. I do not teach so I do not count.
2 friends of mine are assisting the aforementioned expert in asana and pranayma so perhaps they will instruct me soon.