there are certain forms of contraception that you cannot use over an extended period of time (such as the injection depo provera - no more than 2 years) but oral contraceptions have no time limit. I've used mine for 7 years and I know I'm still fertile.

Your best bet would be to go to your nearest clinic - you and your wife - and research your options with a nurse. Any nurse will tell you that two forms of birth control is always best. For example, if you use a condom, also use spermicide because condoms can break! Unlike what has been said here, they are not the most sure way of preventing pregnancy.

Again, the best thing is to do lots of research with your wife and get some advice from a clinic doctor or nurse.

And for the record, I think depo provera is horrible and should have never been allowed onto the market.