Curious to know if anyone has a seo tasklist to be completed each month? Please advise. Thank you.

I think there is no such thing, if you have a site and you do the seo work and site maintains the position. You don't need to do anything.

I see a lot of site with no seo going and the still high rank.

I do think there isn't a these kinds of factor, should you have a niche site and you also do this search engine optimization perform in addition to web page maintains the positioning. You should not do whatever.