James,
You have the right way of thinking.
OK, maybe you made a slight mistake going for these in the first place, but if they are doing the job, then stick with them until they won't do what you want any more, only then consider replacing them with something a little more superior. My ones (both metric and Imperial) that I had like yours went with the old mill when I sold it, I then upgraded (so I thought) to ER.
Just as a side note, I have a full ER system, both metric and a few Imperial, but very rarely use them any more. I have outgrown them, and now prefer to use spindle collets instead. The ER's have been relegated to more menial tasks.
It is just a matter of natural progression in our little world of home machining. No matter what anyone else thinks, use what you have, and be happy.
Bogs