The 2 x age launches might be a bit pessimistic for older pilots. I started gliding aged 40 and took 75 launches (mainly winch) to solo. If I'd trained entirely on aerotow I think there would have been fewer launches.
However, it was then another 7 years to complete a 300 km flight!
I suspect we all agree that the most important thing when learning to fly is flying frequently - if you only fly one day a month learning gliders, you might never go solo.
[The problem I found as an older trainee is that work gets in the way of flying, thus the 7 years]