\documentclass{article}
\begin{document}


\def\now#1{NOW #1}

\def\later#1{LATER #1}
\edef\expanded{\now{a} \later{b} \noexpand\later{c}}
\def\later#1{MUCHLATER #1}

Expect: NOW a LATER b MUCHLATER c.\\
Got: \expanded.

\def\later#1{LATER #1}
\newtoks\tka
\tka={\later{b}}
\edef\expanded{\now{a} \the\tka}
\def\later#1{MUCHLATER #1}

Expect: NOW a MUCHLATER b.\\
Got: \expanded.


\def\later#1{LATER #1}
\newtoks\tka
\tka={\later{b}}
\def\between{BETWEEN }
\edef\expanded{\now{a} \expandafter\between\the\tka}
\def\later#1{MUCHLATER #1}

Expect: NOW a BETWEEN LATER b.\\
Got: \expanded.


\def\later#1{LATER #1}
\newtoks\tka
\tka={\later{b}}
\edef\expanded{\now{a} \expandafter\noexpand\the\tka}
\def\later#1{MUCHLATER #1}

Expect: NOW a MUCHLATER b.\\
Got: \expanded.



\end{document}