I certainly wouldn't want anyone to go off on their own after less than 4 or 5 hours on taildraggers, and those 4 or 5 hours better consist of at least 50 landings on various surfaces and fields both short and long.
I certainly second that! I think that in those first few hours, you're still flying on luck. There is a large attitude shift required over tricycle flying, in that directional control is vital, and you don't stop flying the aircraft until it is tied down. For most tricycle pilots, it's going to take more than 5 hours to assure these careless habits are trained right out for good.
There's a difference between being on your best behavior, new flying a type, and being ready to take it somewhere solo, and deal with whatever might come up along the way. If after "checkout" a few hours of solo circuits in different wind conditions, on different days, then okay. But you're not checked out, until you're comfortable with it all.
I had to check myself out in a Tiger Moth a few years back. It had not flown in ten years, and a maintenance test flight was required. There was no one else to do it. I was on my very best behaviour, and waited until the wind was perfect on the grass runway. I did my few flights (and a few circuits for my sake) and all went fine, but I never yet the conditions gang up on me!
You should feel comfortable when you can happily land on one main wheel first in a light cross wind, hold it there for a moment, land the other main wheel, pause more, then the tail wheel. When you are equally content to threepoint or wheel land, then you're ready....