align text after formula in separate equations

Question

I have some text following equations that are separated by paragraphs (so I can't use \intertext). I would like this text to be aligned horizontally in all of the equations in the document. Example:

\documentclass{article}
\thispagestyle{empty}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
  a_i + b_i = c_i
  \qquad \text{for i = 2, \dots, 9}
\end{equation*}
Then a lot of text follows.
\begin{equation}
  k_i = a_i + b_i + \sqrt{\text{some stuff that messes up alignment}}
  \qquad \text{for i = 1, \dots, 7}
\end{equation}
\end{document}

where I would like the for to be aligned.

Answer 1

This solution centers the first equation in the space taken by the second equation.

\documentclass{article}
\thispagestyle{empty}
\usepackage{mathtools}
\newsavebox{\tempbox}
\begin{document}
\savebox{\tempbox}{$\displaystyle k_i = a_i + b_i + \sqrt{\text{some stuff that messes up alignment}}$}
\begin{align}
  \mathmakebox[\wd\tempbox][c]{a_i + b_i = c_i}
  \qquad &\text{for i = 2, \dots, 9} \notag
\intertext{Then a lot of text follows.}
  \usebox{\tempbox}
  \qquad &\text{for i = 1, \dots, 7}
\end{align}
\end{document}

Answer 2

\documentclass{article}
\thispagestyle{empty}
\usepackage{amsmath}
\begin{document}
\begin{align*}
  a_i + b_i &= c_i
  &\qquad \text{for }i = 2, \dots, 9\\% math mode here!!!!
\intertext{
Then a lot of text follows.
\endgraf
and more
\endgraf
a third paragraph
}
  k_i &= a_i + b_i + \sqrt{\text{some stuff that messes up alignment}}
  &\qquad \text{for } i = 1, \dots, 7% math mode here!!!!
\end{align*}
\end{document}