It's been a good 2 years for me and I am still considering myself a beginner:) I think it's more about the daily amount of time spent to learn and practice trading.
Honestly the learning process of trading has no limit even after becoming a profitable trader, personally I am a self taught trader after spending many years studying the chart I haven't reach my desire goal and I am motivated to continue with the learning process yet because of mixed results i.e profitable and incurred losses as well, I believe once the trader started to earn profit consistently then such a trader would concentrate more on trading while using limited time to add or gain more knowledge, however the lifespan to becoming a profitable trader would depend on fast the trader was able to apply and implement everything learnt into live trading thus it's more like individual rate of understanding of how to trade.