Sente first move advantage

I was wondering what others thought about the first move advantage sente has, namely how much of an advantage it is, how long you think it can reliably be held onto, etc.. There aren't enough games on record, especially between players of very close caliber, to come up with precise conclusions that way.

If I had to guesstimate, the first move advantage leads to about a 58-42 split. It can take 80+ moves against solid play to narrow the gap with gote, if at all. If both players are playing inaccuracies, of course the first move advatange is worth much less.