Some do?

https://www.itv.com/news/2024-11-20/why-is-the-use-of-anti-personnel-mines-in-ukraine-so-controversial

Some mines are designed to have a time limit on them and become inactive after a set period of time.

However, other mines can remain active and dangerous for many years after the conflict has ended.

According my linked article:

US officials says the mines they send Ukraine will be “non-persistent”, meaning they have an internal mechanism to shorten the lifespan of the trigger.

The mines are designed to become inert after a set period of time ranging from as little as four hours to two weeks, officials said.

They say the mines use an electrical fuse that requires a battery, and the mine becomes inert when the battery runs out.

The US intends for Kyiv to use the anti-personnel mines in the eastern part of the country, US officials said, where Russian troops have made slow and steady progress against Ukrainian defensive lines.

Ukraine has also made assurances they will try to limit the risk to civilians.