A steep discount trades for a 30-second reclaim window.
A sound trade only when the workload's architecture already tolerates it.
Fits Spot
Batch processing, fault-tolerant, checkpointed work
Never Spot
Anything that can't tolerate an abrupt, short-notice termination
Live migration and Spot preemption solve unrelated problems: a standard VM's MIGRATE policy survives host maintenance transparently; a Spot VM gets no such protection at all. Instance flexibility now lets one MIG span several machine types/Spot mixes, favoring the lowest observed reclaim rate.
Editing an instance template never touches instances the MIG already created — a rolling update must be explicitly triggered.