Not harsh at all, this is the nature of the scheme - it's the way it works. Look at all those golds who routinely ratchet up 2 - 3k points a year - if they could roll over the excess points then the implications to BA would be severe. There's a minimum level for silver and a place to go to beyond Silver. BA is not a charity, equally you can vote with your feet too.

Having said that, are you not a teeny bit tempted to do a bit of low cost tier runs to hit the magic 1500? And isn't that the point?

You won't get the points back by ringing up, the nearest you would get is a bit of a time extension if you could get gold just after your membership year.