In most cases, a type rating lasts 1 calendar year and begins on the last day of the month during which you obtained the qualification. So, for example, if you were to earn your type rating on the 19th of April 2021, the official commencement date for your license would be the 30th of April 2021. The type rating would expire on the 30th of April 2022.
The exception to this rule is single-pilot type ratings for single-engine aircraft. These type ratings last for 2 years under the same regulations. Therefore, in the above scenario, your type rating would begin on the 30th of April 2021 and expire on the 30th of April 2023.
Once your type rating expires, you will be required to complete a session of refresher training and a proficiency exam to renew the license. This helps to ensure that essential knowledge is not forgotten over time and that specialized pilots remain proficient to the highest standards.