First, you should have posted this question in B4i section.
If you bought 2 months license or package, you get a license to start using B4i and the software can be use forever. If you are lucky, you get to download a free version before the 2 month period ends.
B4X products get updated quite frequent. So you will want your version updated all the time. You may want a piece of mind. Someone may share a project on this forum later that you want to try but it only support the latest Core library. If you are lucky, you can have a workaround but my experience is I can’t make my older version of B4i work without upgrading.
If you do a math, it is more worth to go for the 2 years package. You may try to get the 2 months package once and I predict you will ultimately go for the 2 years. I always purchase the 2 years package and always renew to the 2 years package.