I have got the answer to the profile validity from another post . Here is @vik 's answer.
“Your file is kept in the pool for one year during which time there are multiple draws (selections) and you can be picked in any one of those. If say your points do not make the cut and you are not invited for a year then your file drops from the pool and you have to re-apply next year.”
Also @vik, as I am new to this forum, Please let me know if there are any posts such as " Read this master thread First / Read this posts first". It would be helpful for both of us. We can save our time and you can avoid answering the the already answered questions.
Edit 2 :
I have got the answer for updating the CRS profile also from another post
Yes you can modify your application at anytime provided your eligible for the pool. If you’re not then you have to reapply.
Candidates are picked from the pool every time they do a draw (the time schedule is up to them). Your application can stay in the pool for up to a year.”
More information : http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=1005&top=29