Another "depends" answer here.

I didn't even know about charting until we had been TTC#1 for 8 months. We ended up getting a referral to a specialist after 12 months and I was then very annoyed when the GP suggested we had only been seriously trying for 4 months because I had only been charting for 4 months. As far as I was concerned, we had been seriously trying the day I stopped BCP... The reason I was so annoyed was because we had seen the GP for a pre-TTC appt 3 months before we started TTC and she had never mentioned charting, so for her to turn around and say we hadn't been trying seriously because we hadn't been charting was very hypocritical!

When my sister started TTC last year, I encouraged her to chart from the beginning. She had always had irregular cycles before going on BCP, so I thought it would help her. Turned out to be a very good move because after 3 months her cycles became annovulatory and once she had charted 3 annov cycles in a row she was able to take those charts to her GP and ask for assistance.

If your cycles are regular, you're having sex regularly (at least every 2-3 days) and you are ovulating reliably, there's very little need for charting.

Of course, it could be worth charting for just one cycle to confirm that your cycle is following the pattern you think it is. I was caught out when we started TTC#2 because I figured after 3.5 years TTC#1 I knew my cycle well enough to not need to chart. When we started TTC#2 my cycles were the same length as when TTC#1, so I assumed I was O'ing at the same time. Turned out I was O'ing later than I thought and had a shorter LP than before, so our timing was off by about 4 days the first couple of (non-charting) cycles...

So, how long do you wing it? Well, how long do you want to?