Garage upgrades last for varying amounts depending on what they are and the amount of time they would typically last in real life.
To view the remaining uses and potentially upgrades that need repair, click on the Garage option under the Office menu. Then choose the Upgrades tab in the Garage. The remaining uses are listed on the far right in the list of garage upgrades.
Any time an upgrade is used in a repair, overhaul or building of a part, it's use count will decrease. When an upgrade runs out of uses, it will either have to be repaired or replaced (indicated with red text). In addition, some upgrades require that another upgrade be functional. If one upgrade breaks, then any upgrades that rely on it will also be temporarliy unavailable (indicated with yellow text.)