Well to completely go without conversation? not including family? I will answer both in the hopes of answering the question in its entirety.
When I was growing up, I struggled with social interaction with my peers and with society in general I was socially awkward, I struggled with mental illness and was never treated for it until later on in life. My family thought I had an overactive imagination I used to have no friends, because I used to have hallucinations and hear voices (according to clinical mental health) so you can imagine how awkward I was growing up. My parent used to isolate me as much as possible from interacting with others, she used to lock me in my room I spent many hours drawing, reading playing video games I had little contact with the outside world though I had my personal family so in this time no interaction with peers or others outside of my family for maybe 12 years? Give or take about this much time lapse.
When I reached my teenage years (17 years of age) I was kicked out of my home and struggled to find a stable place to lay my head. I was homeless had no family around me where I was at around this time. I didn't talk to many people on the street the area I was at they were not the best people there was many times where I witnessed different acts of crime, abuse, theft, vandalism I even witnessed a murder (which I won't go into) in this time of my life I did not talk to others for 3-4 years.
Then around this time I found (or they found me to be correct) my other parent's side of the family, I was able to have a roof over my head finally. But around this time, I was so used to not talking to others and had PTSD, depression, night terrors, social and regular anxiety (this is not including my mental condition, which got worse from my experience of being homeless.) But there were ok times I found employment here and there. But was never really able to hold stable employment due to my condition (at this point in life I still did not know I had this condition). During one of my jobs, I had to relocate to Northern California up in the mountains I found solace in nature and started my spiritual journey (I was already spiritual this is just when I was able to find tranquility and explore it further) I started researching different religions and different practices, I practiced mediation for the first time. I could go on but for the sake of answering the question 12 years without interaction with non-family, 3-4 years total isolation (if you don't include hi, bye, thank you.)