There's one exception to this rule, that I'm aware of and it relates just to the original virtual MX 'devices' (VMX100 in Azure, AWS etc.)
The licences for these are, in effect, also the devices - and you can no longer buy them (they are End of Sale, replaced by more capable and flexible VMX-S/M/L). When your co-termination date arrives, therefore, you cannot include them in a Dashboard renewal. If you do just renew - even if you include (say) a VMX-M (functionally equivalent, scale-wise, to VMX100) - your Dashboard will show: VMX100 License limit 0 Current device count 1 (or more) and you will be non-compliant, licensing-wise - and thus, into your 30-day grace period.
If you have VMX100s, you need to plan to deploy new VMXs (small, medium or large, cloud-platform dependent) and a migration of remote peers from one to the other, in advance of your co-term renewal.