Have you ever flown thousands of miles to surprise a friend or relative? What was their reaction and would you do it again?

I have a friend in Tokyo who is very ill, chances of his survival more than 3 years are 50/50. I plan to visit him in June and would like to tell him of my visit. The one problem is that this trip is unplanned and not in my budget for this year, so I might not be able to afford the trip come June, I won't really know if I can afford it until the day before my proposed departure. If I tell him about my plans to visit and then have to cancel he will be horribly disappointed. Right now I'm thinking of purchasing a ticket and if I can afford the trip in June I could surprise him, if I can't afford the trip he won't have to face the disappointment.