My wife is preparing for military deployment.  She has been advised
that taking birth control pills to avoid a menstrual cycle is safe as
long as she has at least one cycle a year. Is this safe?

Yes, it is safe for most women. Here are some links about this practice:
http://www.ivillage.co.uk/health/whealth/repro/qas/0,,180663_183697,00.html
http://www.thestranger.com/2003-09-18/feature.html

However, if she has any kind of kidney, heart or other problems or if
she smokes, it is worth noting that the pill increases risk of blood
clots and most doctors won't prescribe it in those cases. Myself, I
have mild kidney disease which disqualifies me from using the pill.
:-(

Good luck to you and your wife!

I strongly recommend that she try it for one cycle before deployment,
if possible.  Individual responses to artificial hormones can vary
widely!

When I took "active" pills continuously for only 5 weeks I experienced
severe emotional disturbances.  In my opinion, it would be far less
troublesome to have a menstrual cycle than endure this emotional
duress while trying to function in a combat zone.

In addition, I have read that some women experience bleeding or
spotting despite taking active pills continuously.

I hope she finds a compromise she can live with!  Best of luck to both of you.

I have heard that the Depo-prevara (spelling?) can stop your cycle for
6-months at a time.  Perhaps this could help?