There is no such thing as short-term SEO. I'll say it again: There is no such thing as short-term SEO.
SEO is an investment; it has to incubate before you see any results. No one ever listens to that. People see great results after a short-term period and decide to call it quits. They think that short burst of work will sustain their rankings forever.
The people who think they can do SEO for only two months, stop and sustain results are the same people who think they only need to workout for two months to always have rock-hard abs.
You'll start off looking like this:
"I knew I only needed two months of Body Builders Extreme
To The Max. Screw those guys, and pass me the Cheetos."
"I don't know what happened. I went to the gym 2 months ago and looked great."
Wait, what? You mean Matthew McConaughey works out EVERY DAY to get those abs? You mean I have to keeping doing this if I want to keep seeing the results? You crazy, girl; you crazy.
But wait! There is method to my madness! Like any good online marketer, I can prove my ramblings thanks to my handy-dandy analytics. Let me tell you a story.
We had someone, we'll call them Wooderson, ask us for link building help. We obliged and helped Wooderson's site reach 20K visitors in a month. Wooderson was happy. We were happy. Then Wooderson decided they didn't need to do any more SEO because they've achieved their goal. We tried to negotiate, but their mind was made up. So we parted ways. Then this happened:
Rankings dropped. Traffic dropped. Revenue dropped. Wooderson was not happy, and we thought those four little words that agencies just love to use.
We told you so.
Have faith in SEO. Don't stop just because you've seen great results. Without constant work, you will get flabby.