How old do you have to be to become effective in speed reading?

Dear Roba, == I think Speed reading is a skill that can be learned, not acquired.
It mostly involves breaking poor habits that we may have developed since we learned to read.
Simply becoming a faster reader isn't the point, either – you want to become a more efficient reader.
== You will get your reading speed as soon as you have finished your timed reading.Unfortunately, since the age of12, most readers do not substantially improve their efficiency and never reach their full capacity.
== This issue does not mean you have to old, well- life experience, a Professor in a college or even Intelligent to have Speed Reading skill and being blunt in its practice.
You have to have the "right kind of brain".
== While virtually anyone can "master" the speed building exercises to become aware of the presence of words at high speeds, few can take speed reading to the next level to make it genuinely useful.
The main issue is whether a person can develop thinking habits that are at least an order of magnitude faster than the rate at which he takes in words.
== We can raise, promote and develop this skill in our children when they begin their education and leading them to comprehension practice.
When children first learn to read they have no comprehension.
After reading for years they develop comprehension.
== When someone learns speed reading techniques, they must first learn the mechanics and speed, then they develop comprehension.
This is no different than a child learning to read the first time.
They learn to pronounce words, the mechanics, then when their brain can process this automatically, they learn comprehension.
== It is common for high school children to only have a50% to70% comprehension rate at normal reading speeds.
Speed readers often report a50% comprehension rate after a few months of practice.
I hope I've got your question point

Read completely and don't do skimming and scanning. This will help you to increase your vocabulary and grammar expertise, in result your reading speed as well as comprehension rate will increase remarkably.

It doesn't have anything to do with your age, it does with your experience in the field!