How many years should you be on birth control?

Only if it is a 28 day pill.

If it is a 21 day pill one or 2 months of not taking the week break won't do much harm, but it shouldn't be done on a long term basis. Many women do this when they are going on vacation etc and want to avoid a menstrual period.

If you want continuous easy protection you may find the Depo injection easier to cope with, this also has a common side effect of preventing menstruation.