Have you asked licensing@meraki.com or support whether they can convert te remaining license time? Afaik this should be possible. Refer to the FAQ:
https://documentation.meraki.com/zGeneral_Administration/Licensing/Meraki_Licensing_FAQs
Do I have to buy more licenses every time I buy new hardware?
Not necessarily; licenses are sold separately from the hardware. For example, you could upgrade from the MR18 to the MR33 without buying new licenses. If you upgrade hardware to a model with a more expensive license, say from an MS225 to an MS250, you can use the “Upgrade” tool to convert the license. The difference in cost between the licenses is made up of time so you will lose some time as an MS250 license costs more than the original MS225 license.