Does patent invalidation often happen?

If you are an invention patent, there is almost no possibility of invalidation, because the invention patent is authorized by the examiner after the global search and substantive examination of the existing technology confirm that your technology is patentable.

So don't worry about anything.

Of course, if you are a utility model patent, because it is registered, it is more likely to be invalid without substantive examination. But it also depends on whether your patent hinders the development of other people's production and sales. If there are no obstacles, no one will be full and spend money to invalidate your patent.