参考：
Extending side margins for Title section in IEEEtrans document class
Latex: IEEEtrans模板下 扩大标题宽度
通过\parbox关键字可以实现扩大标题宽度的目的，例如：
\documentclass[conference]{IEEEtran}
\begin{document}
\author{The author}
\title{\makebox[\linewidth]{\parbox{\dimexpr\textwidth+2cm\relax}{\centering I want to make a title that its length is adjustable and that can span into maximum two lines instead of three now}}}
\maketitle
\end{document}
呈现如下：