@transdelionI did away with the two years options.
A year after the introduction of the two years options, it became clear that it was a mistake. Many of those who supported the site with one year memberships switched to two years memberships. So the first year was great. And when things are going well, one tends not to questions them. Well, _I_ didn't.
The first year was good enough that I started looking around for a programmer to hire to pick up my slack. However, when the anniversary came, the site's income dropped significantly, making the hiring of a programmer on permanent basis unfeasible.
So to even out the site's income and make it stable, I removed the two years option so that there is no good year followed by a terrible year, and make sure that I can pay the potential hiree every month of every year.