I reached out to the LTR folks (thanks Tod) and this was there reply: "After successfully collecting the visa from oversea, you can enter Thailand at any time as long as your LTR Visa still valid." So I should not have any issues.
I appreciate the different perspectives on where to get the visa. Everyone is applying with their own unique circumstances and it is nice that they offer some flexibility. Maybe I will check back in here in a year or two to share some real world experience of having opted for the eVisa. In the meantime, I look forward to completing this last step and starting my retirement in Thailand.