I know that SEO task should be regular done but is there any time limit for it? How much should be devoted for SEO work?
It is depend on scale and volume of your jobs. I have spent 10+ hours daily in overall SEO process, including link building and content creation. I have not done it all myself and many jobs have already been outsourced. But still, a huge time consumed daily anyway.
i don't think u can have a time frame for it ... everytime i create new post, i do this : 1. Upload/post new post. 2. Social bookmark the page. 3. rebuild sitemap. 4. Ping. 5. Build link
Usually I focus on link building and less on content creation. Since link building takes time for SEs to consider.
that would depend on your competition. if you are in an extremely competitive field, then you will need to spend a LOT of time. if you have low competition, then few hours to begin with and then few hours here and there would do the job
Sorry, but that's terrible advice. If you have a million links to your site and you've got a few #1 rankings, what good does it do if your content is terrible? Content should be your priority on any site. GOOD content or else your SEO efforts will fail you. As far as time - this is completely on a person by person basis. There's really no way to tell how much time you spend on SEO. You could take the easy road or the much more professional route.