clarification on lifetime options

I 've had a BF2023 Lifetime 5G plan for a couple years. Been working great. I am in the process of migrating some other email accounts to mxroute and want to understand a few things

Can the "BF2023 Lifetime 5G" be stacked with a newer option like the "2025 Lifetime 15G"? Just curious. I assume not, but more generally if there are any options to upgrade the BF2023 or get credit for it toward another plan if I didn't want two different plans?