How long will it take to reach a writers level of Grammar usage?

i dunno there awl fikk ear

I'm not sure about Grammar, but since Granpappy started using the Geritol, he's been out of the old out house in pert near 20 minutes. Hope that helps.

Grammar isn't difficult.

You don't have to be a writer to be good at it.

You either know it or you don't. If you don't,then learn it.

You should know it by the time you leave school,anyway.

It depends of too many factors to give an answer that's useful!
Such as what level the person is on at the moment and what kind of aptitude and time and help will be given.
Also, more importantly: what it is that you consider a writer's level of grammar usage.

For how ever long you practice. Do remember though that their are that many Pedant's out there and sometimes even though you feel you have a good grasp of grammer, they will still pick holes in it as it does not fit right with their interpretation of English use.
A little tip always read out loud what you write, and see if it sounds right. This is also good for syntax and puncuation too. Hope this helps.

Could take years.

Depends on where you start from, how much u know, how much u study. The best, fastest way to learn grammar is to study a foreign language. Once you are trying to understand another language and see how differently a language can be structured and have to think in the other language, you begin to understand and remember grammar rules much better, They are the decoding devises of languages. Also writing daily, as in a journal or working on the school paper or on a story or novel, forces you to learn the "rules of the road," esp. if your teacher or someone who knows grammar reads what you write and tells you what mistakes you make. That sharpen your skills quickly.

Depends on what you consider to be acceptable level of grammatical usage. Grammar is used by,all every day. Correct usage of grammar is a different story. You will find that writer's will generally have a team of editors to spell check, rearrange any parts that are out of context.
The best way I've found is to read as much as possible. By this method you will automatically retain the written word and how it is used and in what contexts.
Read aloud to yourself, and force yourself to read every word, NO speed reading as you only gloss over the words.

Read. Read everything. Novels ,articles, Shampoo bottles, Cornflakes boxes. Old books new books. good books and bad. mills and boon and andy mcnab. ( i didnt mean that to rhyme but ill leave it in )

the more you read the more you instinctively know what is correct and what isnt when you write. Remember " writers level grammar" isnt a set of rigid rules that have to be adhered to strictly. they are there to be bent and moulded into your own style of prose etc. otherwise every piece of writing would be the same and ultimately Shite and boring to read.