I haven't used them in years, but never had a problem as long as
the bottle was dedicated to one chemical. The only time I ever
had issues was when they were used for different chemicals.
They're very difficult to clean. Residue gets caught in the
accordion folds, and is almost impossible to clean thoroughly.
Last year, I was given some accordion bottles. After trying to
clean one (in extremely hot water), I hack-sawed it in half.
There was all sorts of residue in the folds.