Let's start by saying answers to your question will differ based on local geography and the local SB population for each of us.
For me, I have stopped agreeing to travel for a 1st time meet more than 25 miles. I have all kinds of stories from my time living in San Jose and travelling to San Francisco, Modesto, or Oakland for M&G's. And still more from my time in the San Fernando Valley travelling to Downtown LA, South LA, Pasadena and Thousand Oaks. The net-net from all those was a 95% failure to get to BCD. Note that on rare occasions, I have agreed to cover Uber costs after (i.e.: if) she arrives. One was coming from Rowland Heights - which is 60 miles and a 90 minute drive from my home. She messaged me 1st on SA, was willing to pay her own Uber, and only wanted $2.5 in allowance. Plus she had fresh test results and hated condoms. Seems too good to be true? Well, she delivered on everything she promised. But her looks "face to face" (or ass to face

were somewhat less than I was hoping for. Maybe a 6.5. It only lasted 3 or 4 sessions.
Caveat: In my area, there are plenty of legit SB's who live within 30 miles, and are happy to travel to me for BCD dates. At any given time, even in down cycles, there are at least 2,500 profiles that fit my specs. When I contemplate a M&G with a POT who is more than a 15 minute drive, I ask her to meet me somewhere half way between us.
But in your location, PaPa Sweet, I can understand the need to deal with greater distances. My advice is similar to those above; you decide how much TIME and CASH you are willing to invest in a M&G. Then avoid committing the cash until the last possible moment - and presumably only if you have some indicator/confirmation she will show up.
Also, I'm surprised by your comment about moving to text. From the "tone" of your conversation with her, I thought you were already messaging offsite.
And finally, to directly answer your question; the longest I ever travelled only for a M&G, was 90 miles - San Jose to Modesto (note to all: NEVER travel to Modesto! Just don't! You have been warned!). And as you might imagine, she was an 18 year old, Latina hottie, with real life strict father issues - AND she had a friend who wanted to "experiment." The end result: Nada, plus I lost $400 in wasted hotel costs, gas, and Starbucks drinks for her that ended up in the trash.
Life is good
The Cat