Hi,
I'm a 32 year old guy and I underwent treatment with Dr Tan for 2 years before we finally got the good news in June. Our baby is expected to be delivered in March next year =) Shall share a bit of what I know below.
Regarding progress, you can do a SA every half a year or more frequently if you want to. For me, the progress wasn't amazing, like 2% jumped to 3%, but I just maintained faith because the results were already better than before treatment. Of course, 1 year in, I started having doubts. But I just continued and also supplemented by visiting Dr Lim Kok Bin at Raffles Hospital. He gave me pills that increased my testosterone levels and the medication didn't clash with Dr Tan's.
Again, in terms of SA results, there wasn't very clear improvement, but any improvement was already welcome. Kept persevering up to about 2 years. Just when we were about to give up and visit a polyclinic for reference for IVF, the good news came.
Long story cut short, have faith, although it may take long. No matter how low the chance is, there is a chance. So keep persevering unless time is really an issue for you.