  An upper limit on $n-\bar n$ oscillations can be obtained from the stability
of matter. This relation has been worked out theoretically and together with
data yields $\tau_{n\bar n} > (1 - 2)\times 10^8 sec$. A recent publication
claims a different relation and finds a nuclear suppression of the $n\to\bar n$
oscillations which is two orders of magnitude weaker than the previous
evaluations. Using the same approach we find, nevertheless, that the earlier
estimates are correct and conclude that future experiments with free neutrons
from reactors are capable to put a stronger limit on the $n - \bar n$
oscillation time than experiments with large amount of neutrons bound in
nuclei.
