Throwing out the rubbish is the hardest thing

Time and time again it strikes me that much software would be improved by asking the question at the design state `when do we expect to throw this way' and budgeting for that. How often do you have to deal with a plain out-of-date system that is absorbing massive amounts of its creators effort simply to keep running? Fairly often if you have anything to do with UK public sector systems. My favourite example this week: government gateway logins for the inland revenue are incompatible with ones for VAT - what?

Anyway. Something to add to your list of design principals when you are designing software: write down the criteria for throwing the system away before you get locked in. You'll be glad you did.