I wouldn't hesitate to fill a 5 gal barrel with 12-13 gal crop, but only if you plan to sell it. I had 50% of my sales 2 years in a row selling bourbon barrel aged maple syrup. It is a fantastic value added product. You can take 5 gallons of maple syrup, which you might sell at $17 or $18/qt ($340-$360 less container cost) and fill 200ml flask bottles (about $.90 ea) and get $1128 less bottle cost which is still over $1000. Read my posts on how I do it. If you're in the "I won't sell any, just giving it away" crowd.just keep it as maple syrup.
Or try what Crooked Cellars Farm did, buy a 2.5 gal new barrel and season it with bourbon. Doing that I see no reason to season it as long as they did. I'm just guessing but I would think a month aging with about 1 qt, or so of bourbon in it, turn the barrel every 2-3 days. Then drain it and fill with maple syrup. Because of the char in the barrel, the syrup will get much darker, thus I use very dark if I have it, otherwise I use the darkest I have. The bourbon barrel aged maple syrup has no grading (at least in New York State).
I buy my flask bottles here
https://www.burchbottle.com/products...86_product.htm
200ml (6.76 Fl Oz) 24 pack case for under $13.00 plus caps are separate. I forget what they cost, I bought a whole case of then 3 years ago from Burch, still have enough to last another 2-3 years. I think they were about 7-8 cents each for about 3500 in a case. Something like 11-12 cents individually for smaller quantities. That 3 years ago.