Kevin,

   It will be very difficult to convince most people that launching a space 
probe should be done without a budget. Your argument that something useful 
might crop up at anytime is not a justification for such an open ended 
policy. It is up to the scientists involved to show the bean counters that 
on average it is fiscally wise to keep these things going. Otherwise your 
argument is analagous to buying a lottery ticket every day because you might 
win. The science folks must calculate the odds and show that these probes 
have a good chance of winning the lottery.

Dave M.