I typically make between 15 and 20 gallons. Today it is a 25 gallon batch and I’ll be sparging 26 gallons. I think I read in Miller that 45 minutes is a good time for fly sparging (which would apply to a 5 gallon batch). While I personally believe faster is better (to keep the sparge water hot), would 45 minutes also be good for 26 gallons? I’m all for getting this batch done ASAP today.
I would use the same sparge flow rate that you use for your 15-20 gal batches assuming you are using the same lauter tun for consistency purposes.