When to go full-time is an intensely personal decision. Each of us has to make that decision for ourselves, each for our own reasons.
I couldn't wait to go full-time. For me that was what the whole desire to transition was about, and it couldn't come soon enough. I was already 62 when I started, and I didn't want to waste any more time. I was riding the brakes on my transition just to be prudent and not make mistakes, so I decided to wait several months after starting HRT. I figured that once I started to male-fail in a T-shirt, it would be time to do it.
I wasn't yet actually male-failing, simply because it wasn't yet T-shirt weather, but once I needed to wear a bra to protect the girls, I figured it was time.
Passing or not was not a big issue to me. I figured that it would take a while before I passed, if I ever did. In the meantime, everyone I associated with would have to know that I was the same person as that guy, so passing just wasn't an option. The village I live in has a population of only 300, so everyone knows everyone else's business, and stealth is not possible. The environment just took that concern right off the table for me: it wasn't something that was worth worrying about. They would either accept me as I am or not.
That was me. Social dysphoria was the biggest part of my gender dysphoria, so I needed to go full-time as soon as I could. Other people experience their dysphoria differently, and therefore have different priorities. The social environment will influence people's decisions, too. Some places are more conducive to transitioning than others.