Developing the basics for striking takes about 3-8 months with a decent trainer, and becoming an advanced striker takes about 3-5 years.
Learning the basics in BJJ takes about 6 months - 1 year, but learning to be an advanced BJJ guy takes about 7-10 years.
On paragraph 1, I gotta disagree. It takes much longer that 3-5 years to become an advanced striker. I would guesstimate closer to 10 to be genuinely advanced. And striking takes way more than 8 months to become versed at on the count of basics, I would estimate a year at least for the average joe.
On paragraph 2, I agree that it takes several years to become an advanced wrestling/jujitsu practitioner. But the basics probably, again take more like a year IMO to become adept for the average joe.
But that doesn't hold for everyone. Some people are intuitive strikers and can find that pinhole in their opponent's guard and sneak in a knockout punch. While some are more adept at at reading body language and movement, and feeling their opponent out in the groundwork sense of the term.
That varies dependant on how a person thinks and relates their thoughts and action/plans in the encounter. The fact
is that there are so many variables involved in becoming versed at a martial art that you can't say this will take this long, or that will take that long without qualifing it as your personal opinion, or guess...even if that's how it goes for you.