I've lost count, but it must be around 3 1/2 years now.
When I was first married, I was on a KITAS with a work permit sponsored by another company. Prior to that I owned a PMA for 10 years, with KITAS and IKTA sponsored by my PMA. I still had about 6 months on the KITAS when we were married, so I let that run out before starting this long and complicated process of becoming WNI.
First I had to exit the country and re-enter on a Sosial Budaya (kunjungan suami) visa. That was extended once while waiting to process a KITAS (ikut suami). Then 2 years on KITAS to qualify for a KITAP (after being married 2 years).
Then more time has passed processing the citizenship application and getting all the documents passed and signed (it's amazing how much paperwork has accumulated - all going back and forward between provincial and Jakarta offices). Once the SKIM was issued, I was into the "home run" stage.
It's worth noting that the 10 years I held KITAS and work permits with the PMA, plus the one year with KITAS and work permits with another company, were all wiped out when I changed status to "KITAS ikut suami" and you basically go back to square one, so it's a minimum of 2 years before you can get to the KITAP stage (although the fact that I've lived here for almost 14 years was brought up at the interview and worked in my favour).
I'll do a separate post for the interview as this one is getting a bit long!