I agree with Hack. VB6 is already long dead in Microsoft's eyes. Best to start converting now than later. Trust me, you'll never, ever want to go back. I must have talked with dozens of programmers who made the switch, and yes, it was grueling and ugly at first, but after 6 months, none of them ever wanted to go back to VB6.

200,000 lines of code could seriously probably be cut down to 150,000 in .NET. It's just that more efficient. All of my programs got smaller when I converted. Last program I converted around that size took me about 1 month. I started with my smallest programs and worked up to my largest ones.

As mentioned, there's no guarantee your program will continue to run on the next version of Windows. I think Microsoft realizes there are a lot of VB6 programs out there, and for that reason alone, continues their run-time support.