A permit is not a one-time approval that stays valid indefinitely once it is issued. It has a clock attached to it, and if work stops for too long or never starts at all, that permit can become invalid. For a project that is already behind schedule, finding out the permit itself expired is an unwelcome surprise.
Most Florida building departments follow a similar pattern, built around the Florida Building Code's administrative provisions: a permit becomes inactive if work does not begin within a set window after issuance, and it can also become inactive if an approved inspection has not occurred within a set window after the last one. The exact number of days can vary by jurisdiction, but 180 days of inactivity is a common benchmark used across the state.
The important detail is that it is measured by inspections, not by informal progress. If your contractor is on-site working but never calls in for a required inspection, the permit's clock is still running toward expiration as far as the building department is concerned.
An expired permit generally means the approval is void. Depending on the jurisdiction and how much work was completed, you may need to apply for a new permit, which can mean new fees, a new plan review against whatever code is currently in effect (which may have changed since the original permit), and in some cases, opening up completed work to verify it meets code before it can be covered again.
That last part is the one that catches people off guard. If walls were already closed up over electrical or plumbing work that was never inspected, the inspector may require that work to be exposed again before it can be approved.
A permit is only as good as the inspection activity behind it. Long gaps between inspections put it at risk regardless of how much actual work is happening on-site. If your project has been quiet for a while, it is worth a quick call to your building department to check the permit's status before it becomes a bigger problem than the delay itself.