Hi everyone.
So, as a prelude to my question, I suppose I should give a brief synopsis of what I've been doing. I've been practicing yoga for about a year and a half, using Sri Swami Satyananda's book, 'A Systematic Course in the Ancient Tantric Techniques of Yoga and Kriya'. Amazing book, I've worked worked through the first 7 (out of 36) lessons so far, recently started on the 8th. Overall, they involved pretty much basic asanas, nadi shodhana pranayama, surya namaskara, and some meditational techniques like body awareness, anuloma viloma, and, just now, trataka on a candle flame. Also, they've introduced techniques like jala neti and kunjal kriya, which have been great. So far I've had amazing results, never felt better in my life.

In anticipation of some of the replies to come, I know that I technically need a real teacher but I've been somewhat disappointed with the idea of asana oriented classes, and the idea of practicing meditation in a room with 30 other people doesn't really work for me. As far as a guru, you can call me an idealist but I subscribe to the idea that when the student is ready, the teacher appears.

The other relevant detail is that I used to be a smoker. 15 cigarettes a day, although for only about four months, and occasional marijuana over the course of about 7 years. I quit a year and a half ago. You can see where this is going.

My question is: will a history of smoking severely limit my progress in pranayama? I understand that lungs recover over time, but is progress in pranyama mostly based on the physical lung capacity or the mental control of prana? I'm leaning towards the latter because when you have a case where a swami holds his breath for 45 minutes, I think it's pretty safe to say that it's more than just lung capacity at work. But that's not to say it doesn't play a role to an extent. The question is, to what extent?

The reason I'm asking is that I've just recently started incorporating kumbhaka into nadi shodhana and I'm beginning to realize just how difficult it's going to be to get the timing ratios to their final levels. In the above mentioned book, the eventual ratio to aim for is 1:8:6:2 for inhalation:inner retention:exhalation:outer retention. The inhalation also has to be sufficiently slow so as not to create any noise (not counting the noise from ujjayi). For me that means an inhalation of roughly 10 seconds. So when the final ratio is achieved, that comes out to almost 3 minutes for each round of inhalation and exhalation, including the inner and outer retention. In another book on pranayama, Sri Swami Sivananda mentions this as an almost trivial accomplishment and one that can be easily done with practice and "without help from anyone". As encouraging as that sounds, my previous experience still leaves me slightly doubtful.

Right now I can easily do a ratio (in seconds) of 10:8:20, with no strain and without outer retention. Right now I only do 10-15 minutes of pranayama with kumbhaka, since the book recommends not to overdo kumbhaka initially, but I still practice nadi shodhana without kumbhaka for a second time in the evening, for about 20 minutes. The other thing is that over the last year I haven't progressed much as far as the duration, it's always stayed around 12:24 seconds when I practiced without retention, but never going above 15:30. However, I have noticed that whichever nostril I usually have blocked during practice is now much less blocked than it used to be when I started over a year ago, and I often have days where both nostrils are completely open during practice. So while the durations I use haven't increased much, practice has definitely become easier with time.

So, has anyone here achieved ratios like 1:8:6:2, or anything similar? I would love to hear how long it took you and how much daily practice you had to put in. Were there any other factors like diet, etc. that you felt were a significant contribution? I guess I would just like to hear your experiences.