You can stick with your old set for as long as you like. 'They' are trying to motivate us to change by saying there will be no dedicated watch on Ch 16 after 2005, so a Ch 16 shout may go unheard.
If you do upgrade to DSC you'll need a new Short Range Certificate. Schools will try and sell you a one or two day course and an exam at a price that would buy a new storm jib, but IMHO spending a few quid on a DSC book, reading it carefully, then just sitting the exam should get you a new ticket if you're already familiar with current VHF procedures. And even if you fail first time you'll pass second time and still be quids in.
If everyone has DSC and no-one listens on Ch16 how do I call for example a ship heading for me, or a yacht heading into danger or anyone else who's DSC address I do not know.
You are supposed to send a general 'All Ships' message which alerts everyone listening on DSC Ch70 - they are all then switched to Ch16 and you then use voice to talk through the problem! Convinced? I'm not (yet)!
But aren't only certain classes of vessel bound to keep watch on ch13? I admit I would try that first but I seem to remember you can't be guaranteed a reponse and only DSC is 'guaranteed' to wake them up!
The principal benefit from a yachts point of view is that you can connect most DSC sets to your GPS. In an emergency this sends out a SOS complete with your position and continues to do so until someone responds to it. could be a life saver.
The French Coastguard no longer man Channel 16 and the Coastguard will reduce to a loudspeaker watch in 2005. Apart form that you can enter your friends MMSI numbers in your box and they get an alert when you call them.
Current thinking is to hang on until the prices of DSC sets fall from their current levels which I am pretty sure they will. But if you have to replace your set meantime it is probably worth considering and in any case it is now illegal to sell sets which are not DSC capable although they do not have to be fitted with the kit.