Here's another thought. It takes 3 years on average in the western world to complete a degree. The contents of a complete astrological education certainly is equivalent to, if not more than, a 3 year degree in my opinion. Following graduation, it takes another few more years before one moves up the hierarchy. Why should an aspiring astrologer expect any difference from the above scenario?
Anyhow, here are some quotes that state that it takes years to be a competent astrologer.
"It takes years to become a competent astrologer - not weeks or even months - and then it can take more years to build up a good client base." Astro Logos
"It takes years of study to become a competent astrologer" RASA
"It takes years of study and experience in order to become proficient in interpreting the
complete horoscope in terms of character, potential talents, aptitudes, career, strong and
weak points, health, ability to relate to others and so on." Vica Astrology
"To achieve excellence performing a complex task, which reading a chart is, much in the same vein as playing a musical instrument, requires a critical minimum level of practice that continues to come up in studies about expertise. ... If you want to be reading your own chart expertly and share competent insights with friends and family, 4,000 hours would certainly be enough." Astrology Unlocked by Philip F. Young