Compound Vial Life Expectancy

The recommendation for use of the compound is 4 weeks from first vial puncture. This seems a bit unreasonable, especially if sterility precautions are observed and the vial is only out of the fridge to extract the medication. Is the concern just with sterility or also potency? It seems like the desire of the compounding pharmacy is to limit use of the medication drive a monthly cost model. Many on maintenance may want/need to dose up/down during that phase to find what works for them. Not looking for medical advice, just your experience. What is maximum you've been able to extend your single vial use?

Thanks you!!