Argument on General Elections Being Held Every 4 Years

Should general elections be held every 4 years?
The current state of affairs, concerning the general elections, is unfair and biased and should, and hopefully will, be changed. In this paper I will demonstrate a number of points and prove that something must be done.
My first reason is, as I explained above, unfair and biased. The reason for this is because the current prime minister could hold an opinion poll, which says how popular they are at the time, and can choose when to have a general election whenever they are really popular or, decide not to hold an election if they aren’t very popular at that moment in time. Also, if they are unpopular they can change the public’s opinion of them before they hold a general election which wouldn’t be as fair as if they either, couldn’t hold an opinion poll nor had a set date of the general election.
My second reason is that if something happened to one of the other candidates, then he/she couldn’t take part so the current one would hold a general election so that they have less competition, therefore they have a better chance of winning and in turn are unfair. They are also biased because it’s kind of like rigging an election if they know enough people will vote for their party enough to get enough seats in parliament to have their party win.
Now, people who think differently might say that having opinion polls will get who the people want as PM, if they have a set date or don’t have opinion polls then they don’t know if they are liked enough to win so then its fair as a coin toss, but until then it’s as fair as a double headed coin toss.
To conclude this paper expressing my opinion on the matter outlined in the first paragraph, I think that the general elections should be held either at equal intervals, or not having an opinion poll 1 month before the election. If that were to happen, then the general elections, in my opinion, would be made a whole lot fairer.