Activate new SIM on S9 or keep old one?

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So my new S9 should be arriving today or tomorrow … it’s my first SIM phone to SIM phone upgrade (previously I have Verizon with CDMA, no SIM cards).

The S9 will come with a new T-Mobile SIM card, I’ve heard conflicting advice about this. Originally I was just planning to take the older TMO SIM out of my Galaxy S6 and plop it into the S9, but some recommend activating the new SIM instead.

Any pros/cons I need to consider? Do SIM cards "wear out" or get new tech that I should take into consideration?

Thanks!