I am not a doctor so I can't give you a definitive answer.
My own experience with PBT was that I had prep and then five treatments spread over 2 weeks (early 2020). I was at the Mayo Clinic in Rochester. My prostate cancer was an anterior tumor (front) with little or no involvement of the prostate out covering.
In subsequent conversations I have discovered that the Mayo in Scottsdale (in 2020) was doing (I think) five treatments per week for five weeks. In conversation with my radiation oncologist at M/Rochester he said that more of the doctors in Scottsdale have taken up the five treatment total.
I am aware of other (non Mayo) Proton Beam facilities that use the longer protocol. I don't have the information about whether these facilities have the same equipment to deliver in the same way.
AND, of course what is appropriate is patient and disease dependent.
Its my understanding that the total amount of radiation received is the same with either protocol.
Theoretically, the longer protocol might cause less damage to incidental tissue.
New delivery technologies and the use of the SpaceOar separator (pushes the bowel and prostate apart) may mitigate any advantage to the longer protocol.
A shorter protocol also makes the protocol more accessible to people who can't mange the extended time away from home. In some settings (I think not Mayo) a longer protocol is a 'reason' for larger charges for treatment.

KKP10 I think you and your husband could reasonably ask:
Do any Jacksonville doctors give any patients the shorter protocol? (be pushy about this )
If they do, what is the reason that your husband is scheduled for the longer protocol. (I'm assuming)
What is the current data that supports the longer protocol vs the shorter (i.e. less damage, more efficacious, etc/
Remember that you could reasonably ask for a video consult with radiation oncology doc at Rochester for their opinion about your husbands suitability for the shorter protocol. I could private message you a contact phone number.

and as I wrote elsewhere in connect recently Rochester in the winter is more than OK. Especially if only 2.5 weeks.

Best of luck.