What's tha advantages

with a dexcom CGM, I have been seeing a lot of not so good stuff about MM, but Dexcom seems to be a good fit.
So far after adjusting my basal rates MYSELF, it seems to be working better. All I have been viewing is the disappointments of people with MM.
I am so lucky to be on a MM pump! I HIGHLY DOUBT I will ever be in my target range for more than two days!
For the past 24 hours I have been out of range once, a bit high.243.
How long before it loses its potency after it’s open? And, after it’s opened is it bad to keep the bottles in the frig?