I got out in 1992 as part of the "Peace Dividend" drawdown. The military offered 2 different separation plans, the VSI and another whose name escapes me at the moment. I took the VSI plan. It requires me to be in inactive reserve status for 2 years for every year of active duty in exchange for certain benefits.

You may have signed on for 4 years but your contract called for a total of 6 or 8 years depending on when you enlisted. The other 2 or 4 years would've been in the inactive reserve status. In the event of an emergency, you could've been recalled but that wasn't very likely. The inactive reserves don't require you to go to any drills or anything like the active reserves or National Guard. All it requires is that you keep your locator information up to date.