My longest to date is 38.4 miles, almost a year ago, in OK but varying winds. It was very enjoyable as we (3 AI's) were in areas we don't normally sail (West Maui) but walked funny for a couple of days with that much time in the seat!
Our normal target is 25 miles in 4-6 hours including a lunch break. We have learned that standing up in the AI for 2-5 min. once or twice during a break (Lunch) makes a big difference in how we are move at landing. (Must be old age creeping up on us!
) In perfect winds and course, we could do 60-80 miles plus.
Here our biggest issue is better winds bring bigger waves. 20 mph winds usually rewards us with 6' wind waves. A normal great day out here starts with light winds to setup, then enough wind to sail in for launch and warm up, then building to 15-20's with no waves for maybe an hour where we get our higher speed runs in. Then the waves build and we start downwind sailing up to 4 miles out and back depending on the wind and waves. Lunch off a beach tied to a buoy, a few passes 200-300' off the beaches then with good winds we have our 6' waves to play down the coast for a couple hours of wave surfing and land.
It may sound like we're wild, but we are very safety oriented. We all have FRS/GMRS radios mounted to our vests (always worn), surfboard leashes on all boats we wear for the bigger waves & wind. We carry a Marine radio, an EPIRB, hand pump, 100' throw rope bags each, spare parts, multiple tool kits & first aid kits. Everything is leashed.
Good luck with your regatta plans, wish I could be there.